Looking more like a sleek "they'll never build it like that" concept than an actual production car, the 2007 Mercedes-Benz CLS-Class is what the company calls a four-door coupe. This contradiction of terms is convincingly brought together via the CLS' crouching body, curving side windows and swept back roof line. In a sea of handsome, midsize luxury sedans, the CLS has the increasingly rare ability to stand apart thanks to its head-turning style. And in this segment, that counts for a lot.

Under the overtly athletic skin is a chassis to match. This year sees the infusion of more power under the hood as a pair of new V8s debut. The "standard" CLS, called the CLS550, now sports a 5.5-liter V8 wielding 382 hp, a full 80 horses more than the V8 in last year's CLS500. The mighty AMG version is now called the CLS63 AMG and has a 6.2-liter V8 that makes a monstrous 507 hp, an increase of 38 hp compared to last year. Both engines send their power through a seven-speed automatic with manual-shift capability. Performance is exhilarating in the CLS550, stupendous in the CLS63.

Sexy styling and push-you-back-in-your-seat power are strong draws for moneyed enthusiasts, but the CLS is not without its flaws. The tapered roof line means those in back will have less room than if they were riding in a shorter E-Class sedan. Most passengers will be comfortable back there, but taller folks will want to be quick when calling "shotgun." And in spite of the superb engineering exhibited in the powertrains and suspension, there are some ergonomic quirks, such as a flimsy pop-out cupholder and fussy audio and navigation controls.

Direct competition for the 2007 Mercedes-Benz CLS-Class is hard to nail down, due to the Benz's unique body style. Loosely defined, the CLS' rivals would be V8-powered, rear-drive luxury/sport sedans, such as the Audi A8/S8, BMW 5 Series/M5, Lexus GS 430, Infiniti M45 and Cadillac STS/STS-V. Although all are impressive vehicles, none can match the CLS's impressive combination of style, performance and function.

The 2007 Mercedes-Benz CLS is a midsize luxury sedan. It comes in two trims, the CLS550 and the CLS63 AMG. The CLS550 comes with full power accessories, a sunroof, four-zone automatic climate control, a Harman Kardon audio system with six-CD changer, a trip computer and 18-inch alloy wheels. Mercedes' Airmatic suspension system is also standard and gives the CLS a level of adjustability to suit every type of driver. In addition to the bigger V8, the CLS63 AMG adds napa leather upholstery, heated sport seats, 19-inch wheels, a sport-tuned suspension and more powerful brakes.

Options for both CLS trims include a navigation system, "Distronic" adaptive cruise control, front and rear park assist, "Drive Dynamic" seats (that automatically pump up the side bolsters for additional support during performance driving) and a pair of color-themed "designo" packages. An AMG Sport package is available for the CLS550; it includes 18-inch double-spoke wheels, lower body skirting and paddle shifters. For the AMG itself, there is a Performance package that adds Formula One-style compound brakes, a 186-mph speed limiter (versus the standard 155-mph limiter), a limited-slip differential and even firmer suspension tuning.

The CLS550 has a 5.5-liter V8 that produces 382 hp and 391 pound-feet of torque. The CLS63 AMG has a 6.2-liter V8 that makes 507 hp and 465 lb-ft. A seven-speed automatic with Sportronic manual-shift capability is the sole gearbox for both trims. Paddle shifters are standard on the CLS63 and optional on the CLS550. Responses from the advanced transmissions are satisfying, as there is no lag between shifts, especially in the AMG. According to Mercedes, the CLS550 will run from zero to 60 in 5.4 seconds, while the CLS63 will do that sprint in just 4.3 seconds.

Antilock disc brakes, active front head restraints, stability control, side curtain and side-impact (front and rear) airbags are all standard. Newly standard is the PreSafe system, which, when it senses an impending collision (via rapid braking and steering patterns) automatically tightens up the seatbelts, closes the sunroof and positions the right front seat for optimum airbag protection.

In addition to the prodigious thrust offered by its pair of powerful V8 engines, the 2007 Mercedes-Benz CLS-Class also makes a good showing when the road turns twisty. Left in its default Comfort mode, the standard CLS's suspension responds with typical luxury car motions, soft when it needs to be and stiff enough to maintain complete control at all times. There are two Sport settings designed for more aggressive driving that tighten things up and deliver a full-on sport sedan driving experience when desired. Unlike some other luxury/sport sedans, the CLS invites you to go harder at every turn. Quick steering, minimal body roll and plenty of grip contribute to that sensation. Stepping up to the CLS63 AMG kicks the already impressive performance up a few notches, making this four-seat four-door the equal of more than a few exotic two-seaters.

The CLS' coupe-like body style means getting into the rear compartment is tricky for 6-footers. Once inside, those taller folks may brush their heads, but plenty of knee and shoulder room keep it comfortable. The short windows make it feel less airy than a typical sedan, but compared to a traditional coupe, the CLS is legitimately comfortable in back rather than merely passable. A strip of wood trim that spans the dash differentiates the CLS from any of its siblings, along with smaller, but tastefully applied touches of wood and chrome trim throughout. The AMG version features napa leather upholstery, special multicontour sport seats up front, an Alcantara leather headliner and slick AMG gauges in black on white. As is typical for Mercedes, the audio and navigation systems take some getting used to, as opposed to the systems in Asian competitors, which are usually very intuitive.