Sitting on the Mercedes-Benz stand at the Geneva Motor Show back in 2004, the first CLS astonished styling critics. Even die-hard two-seater fans liked its radical new four-door coupe design. With that hammered roof, arched body reveals and radius-ed wheel openings, the low-slung CLS500 looked more like a snazzy show car than a boring sedan. Then the supercharged CLS55 AMG soon appeared with 469 horsepower.

You'd think that'd be sufficient, but up against hyperquick competitive sport sedans from Bentley, BMW and Maserati, Mercedes-Benz can't remain still. That's the rationale behind the newer, faster 2007 CLS63 AMG.

Absolute power corrupts absolutely
For M-B aficionados, the "63" numerals evoke a glorious past when the Stuttgarters offered the huge Series 600 limousine with a powerful 6.3-liter V8 called "M-100." In 1968, they stuffed that engine into the smaller 300 SEL, creating what was arguably the first European muscle car.

Nearly 40 years later, M-B's high-performance wing is playing a similar card. Intent on having the world's most powerful series-production, naturally aspirated V8, AMG's engineers designed an all-new aluminum block, in house, with different bore centers from the supercharged 5.5-liter engine it's replacing. Displacement is now 6.2 liters (6,208cc). Sure, a blower might have accomplished this power trip more easily, but that wasn't the plan.

Instead, the new V8, which is also seeing duty in the ML63 AMG, CLK63 AMG and E63 AMG, borrows heavily from AMG's racing practice. There's a fully boxed lower crankcase section to eliminate crankshaft flex, ceramic-metallic-coated cylinders (hence, no bore liners), vertical intake and exhaust ports to optimize airflow, dry sump oiling, variable cam phasing and a two-stage resonance intake. From the previous supercharged 5.5-liter V8, output is up 45 horsepower to 507 hp at 6,800 rpm but torque drops from 516 pound-feet to 465 lb-ft at 5,200 rpm.

At our first drive, the AMG engineers took pains to point out that their new V8 is more than a match for the much larger 7.0-liter, pushrod, single-camshaft Corvette Z06, which packs 505 hp and 470 lb-ft of torque. They didn't bother with a pricing comparison. In fact, we don't know the AMG CLS63's U.S. sticker yet, but it should be around $88,000.

Extra-cost options include an AMG performance package, 19-inch wheels (18-inchers are standard), a premium package, bi-xenon lights, Distronic cruise control, navigation, Keyless Go, Parktronic, etc. Order them all and you can add another $24,000-plus to the car's sticker price.

Communing with your fast, the AMG way
Let's not mince words here. This car has 507 hp, which puts it squarely in Ferrari and Porsche Turbo territory. Mercedes says the rear-wheel-drive CLS63 needs only 4.5 seconds to hit 60 mph. And the Benz makes such sprints with minimal wheelspin and no drama. Woooooosh and you're over 100 mph, and heading for an electronically limited 155 mph.

Streaking down the autobahn north of Munich, we flirted repeatedly with 135 to 145 mph, but couldn't top that figure before slower traffic demanded more prudent speeds. The engine fairly sings, and there's a bass woofle from the four big tailpipes (if you lower the windows) that tells victims they've been passed by a serious engine.

At speed, the CLS63 is rock steady, with precise on-center feel and perfectly weighted steering. Although racing influenced the 63's development, it's an adult speedster, not a boy-racer. Out in the countryside, on Germany's winding two-lane D-roads, its handling is taut and precise. You have to work to break the rear end loose; its tire grip is prodigious.

To ensure you can stop with the same aplomb as you'll want to accelerate again and again, AMG has fitted huge disc brakes (the fronts are composite) that are internally ventilated and well-perforated (cross-drilled). They worked well repeatedly on the autobahn, as we reeled in dawdlers, then slowed, before hammering the gas again and enjoying the V8's melodious snarl.

Fast and luxurious
When you're not terrorizing the autobahn in the CLS63, you waft merrily along on infinitely adjustable Airmatic suspension, albeit with AMG's sportier tuning. That said, the CLS63 feels supple, not stiff. While the ride is definitely firm, with virtually no perceptible body roll, it's never jarring or annoying. As you tear through tight corners, with almost no body roll wondering what the poor people are doing today, you find yourself wishing for a "serious" sports model, like a 911 Turbo or F430 to chase. It's that kind of car.

Shift paddles for the seven-speed AMG Speedshift gearbox are conveniently placed and very easy to use. Fifth is direct drive; 6th and 7th are overdrives. You tend to stay in 3rd and 4th on twisty roads when you're flicking the shift paddles for acceleration and compression braking, and use the top three gears on the autobahn for lightning-quick passing. One minor complaint: Unlike the SMG gearbox in the BMW M5, the CLS63 AMG seven-speed does not blip the throttle before downshifts.

Fine leather and matte surface burl walnut underscore the interior's elegance. Nestled deeply below the high beltline, you're further coddled with four-zone Thermotronic climate controls, PreSafe with pre-tensioned front seatbelts and anticipatory automatic seat crash adjustment, Neck-Pro (an electronically controlled head restraint system to reduce whiplash injuries) and eight airbags.

Leaving well enough alone
Other than the CLS63 AMG badging on the front fenders and deck lid, the 2007 CLS63 looks very similar to the preceding CLS55 AMG, arguing that the design was excellent from the outset. All CLS models eliminate the three-pointed star vertical hood ornament, instead the Mercedes-Benz wreath and laurel are inset into the hood.

The CLS slots neatly between Mercedes' midrange E-Class and the top-line S-Class. So all the latest M-B electronic handling trickery, adaptive braking (to flash the brake lights and prime the braking system) and traction control wizardry, some of it adapted from the S-Class, is included.

There's a long spec list that reads like alphabet soup: ABS, ESP, SBC (Sensotronic Brake Control). Brake Assist, Distronic proximity cruise control, and Parktronic parking aids are just a few of its many luxury features. Bi-xenon headlights combine with cornering lamps to point the way around the tightest curves.

Nothing to prove
AMG cars don't scream, "Hey, look at me!" with race-inspired but useless add-ons. Discreet bodywork changes, like the CLS63's aerodynamics-enhancing side skirts, rear apron and trunk spoiler, just hint at this car's high-speed potential. Compared to the BMW M5, the CLS has a tad more horsepower, and a road presence that's considerably more subtle, both dynamically and statically. You can fool people readily in this car; they may not immediately grasp its potential, and that's just what the AMG people probably had in mind.

With a 2007 Mercedes-Benz CLS63 AMG, you don't have to prove anything.