There’s a reason why Bruce Willis fills your television screen every Christmas. People love Die Hard because it’s about someone regular-looking proving much more than that.
Cars are no different. If something unassuming pulls up beside a Ferrari and then suddenly blows off into the distance, it’s like seeing Jackie Chan walk into a bar and kick a boozed-up giant out cold. You’d feel equally bemused and delighted.
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Such things are better known as sleepers. We love them. And when coughing up for a luxury sedan priced nigh-on six-figures, with performance and covert looks thrown in, it’s obvious the Northern Hemisphere does too.

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First up is Audi. The original 100 S4, its first S-badged model, looked less suited to full-berry-giving than it did Uber Black duties (if such a thing existed in the early ’90s), but it’s shaped all its hot four-doors since.
The just-landed B8 S4 is $30K more expensive than the next A4 variant, but singling it out from its cheaper brethren isn’t easy. The A4 already oozes menace with its sharp lines, gleaming grille, and furrowed daytime running lights, so you’d have to zoom in on the S4’s front brakes, in all their six-piston glory, to pick it.

This won’t be easily fixed either with something like an M Sport package. The pack only changes the wheels, grille colour, guard badges, and front bumper. Until BMW offers a factory M Performance variant, this meekly dressed 340i wins this test’s trainspotter prize.

And while those figures no longer correlate to engine size, they hint at the fact that this car punches harder than its formal facade suggests.
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Engineered by Mercedes-AMG, the C43’s ‘AMG’ calipers and drilled front brake discs allude to its performance and help justify its $101,900 ask, without options, while those big eyes, rounded surfaces, and sparkling grille, plugged into its unique front bumper, make it the softest on the eyes here.

Dropped on optional 20-inch wheels it looks positively sexy, though it also brings with it a long options list that takes its $105,350 base price to an eye-watering $125,270, only four grand of which it wears on its exterior.

These cars might be separated only by three cubic centimetres, but it’s the Jaguar’s that feels largest in capacity at the drag strip. Rolling the Jaguar from the line is the best way to manage rear grip and allow its blower to build boost with revs.
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It sets off wailing like its sports car cousin and whining like a supercharged drag car, needing 5.28sec to reach the 100km/h mark before breaking the 400m ribbon in 13.45sec.

However, with luck, and wheelspin, it’ll charge to 100km/h in 5.51sec, before finishing the quarter mile a tenth behind the Jaguar at 13.57sec.

So the needle happily sails past its indicated redline to a 7250rpm cut-out in manual mode, and its torque peak is spread over the widest area from 1380rpm to 5000rpm.
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Mercedes-AMG’s 3.0-litre twin-turbo V6 in the C-Class, contrastingly, goes about this stuff more frenetically. Its 270kW and 520Nm outputs arrive in what feels like rapid gunfire from its nine-speed automatic. It’s geared so short it needs to upshift twice before 80km/h.

As it slingshots forward a metallic howl rips from its optional performance exhaust in Sport Plus mode, punctuated by an abrupt crack on every shift before its 6300rpm cut-out. Triple figures arrive in 4.61sec, 400m passes in 12.87sec.
Switching from the AMG to the S4 is like swapping an assault rifle for a shotgun. Thrust arrives via its ZF-made eight-speed auto’s ratios in thick, linear slugs.
This is partly because Audi’s filled the V6’s valley with a twin-scroll turbocharger, which required flipping around the heads so the exhaust valves point inwards, helping it push 260kW/500Nm through its four tyres.

No prizes for guessing that our all-paw duo ravage the rear-drivers from a standing start. However, roll-on tests flip the pecking order on its head.
The BMW will tear free of the pack from 80-120km/h in third gear, relying on longer gearing and lighter weight to cut it in 3.1sec. That’s a tenth faster than both the Audi and Jaguar, while extremely short gearing lets the AMG down, forcing it to nab fourth at 114km/h and register a 3.2sec sprint.

However, the 340i reels ’em in so quickly at the speed traps it makes you wonder if the petrol station at BMW’s engine dyno facility only stocks 95 RON.
It flies across the quarter mile finish line at 175.56km/h, while the Merc trails with 174.03km/h, the Audi 173.69km/h, and the Jaguar 172.08km/h.

It’s only a shame its suspension doesn’t extend the enjoyment into the bends. Even with low-profile Bridgestones and adaptive M suspension, the 340i fails to tell you what’s happening at a surface level.
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There’s little feedback from its tiller on how much purchase the front tyres have. It also feels like the front strut set-up can’t translate available grip into sharp turn-in, so the stability police show up well before the fun’s even started, yapping at wheels to keep it within the road lines.
It’ll have you scanning the options list for a fix, but the 340i’s adaptive suspension is already pinched from the M Sport package; and the optional M brakes, at $1400 for the set, are the only chassis upgrade.
They won’t be enough to save the 340i from its dynamic woes, but are worth it, as you’ll sail past a few apexes adjusting to the stock set’s underwhelming power.

Then on the way out of corners the LSD-by-brake system sporadically nabs at the rear axle, and as a result, your confidence falls significantly, too.
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Once you find smooth tarmac, though, you can finally let the XE S sink in its claws. The electric steering is sharp, fluid, and commands a front-end that feels magnetised to apexes. It’s here that its firm suspension setup pays off, as you can start to ratchet up the commitment and uncover its huge levels of lateral grip.

Once again, though, the grippier pair prove themselves in another class. The Audi S4 rides so well you’d think Heathcote’s back roads snaked their way through Audi’s test grounds. With multi-links and adaptive dampers all around, it swallows big bumps and high-frequency stuff with pillow-like compliance.
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Even around town, with 35-profile tyres, you’re not afraid to line-up speed humps or potholes.
Admittedly, the Audi’s not the most natural corner-carver against the Jaguar or Merc. The first quarter of steering lock feels out at sea and the nose is a bit pushy, but across a twisting road the optional ($2950) electronically controlled hydraulic diff is so good, it feels like Audi stole the technology from VW’s abandoned WRC operation.

Just don’t try the same stuff in the AMG. Its all-wheel drive system doesn’t have a limited-slip differential at all and shoots 67 per cent of its grunt rearwards. Coupled with its hefty outputs, the traction-control light flickers like a bug zapper if you sink the right-foot as early as you do in the Audi. That said, once straightened, its all-wheel grip allows it explode out of corners.

Switching to its Sport Plus mode cuts out the damper float, and the upside is the C43 feels so tied down you suspect AMG pinched the Merc C63 S’s suspension system.
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There’s an extremely direct front-end connected to a crisp-feeling steering rack. It’s positive, and so rich with feedback that any yaw movements are thwarted with almost telepathic dabs of opposite lock.
And if you’re going to annihilate apexes there’s no better place to sit than in the Merc. The optional Performance seats grab your kidneys tighter than an organ thief, while the raked seating position drops you low into the car.

Our four are each fantastic for cruising in lavishly cloaked performance, and long shall their kind reign. But if value is your guiding principle, the BMW’s a stand-out pick. Short of autonomous driving tech, it boasts the same kit, badge prestige, and refinement as the Audi or AMG for less cash.
The interior also doesn’t seem ‘that’ old, and it’s a sharp looker from the outside. However, its flat seats speak loudest about its undercooked dynamic talent. The 340i’s all about that silken, turbine-like engine, and ignores what the balanced chassis underneath it could be.

One glimmer of hope comes from the $10K discount over its rivals, which could be used toward an M Performance Accessories LSD. Maybe along with a non-variable steering rack (optional) this would have made this a fairer fight for the BMW. However, until the new 3 Series arrives in 2019, this one’s under-braked, out-gripped, and over-powered.
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On the other hand, Jaguar’s XE S injects more handling and grip into the sleeper sedan mix. Meanwhile, a blend of razor-sharp turn-in, dramatic engine noise, and handsome looks mean it has a charisma other brands might need multiple generations to craft.

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When it comes to grunt and drama, however, the C43’s the undisputed king. There’s so much to love about its drivetrain, its gearbox works well when left to its own devices, and it could decimate all if only injected with a proper limited-slip diff.
As a stepping stone between Mercedes-Benz’s C-Class range and AMG’s lunatic asylum, it’s a perfect fit. But crucial ride and power-down issues sink its chances at clenching the top spot.

Yes, the differential is optional, but even without it, the S4’s clever quattro system and thumping drivetrain are strong weapons in its arsenal – the noise also shows it still knows how to have fun. And once you’re done terrorising tarmac, its delightful ride and smart interior bewitch you into its driver’s seat for the drive home.

The S4’s fast, reasonably priced, technologically advanced, and matches this all to subtle good looks. Forget Bruce Willis, the S4 slides onto scene like Superman. Wearing glasses and a smart, business savvy suit, but brandishing otherworldly powers that need to be driven to be believed.