The 2007 Mercedes-Benz S550 sports a 5.5-liter V8 that makes 382 hp and 391 lb-ft of torque. In testing, we've found that this is enough for a 6.1-second 0-60-mph time. A standard seven-speed automatic transmission routes power to the rear wheels. Opt for the S550 4Matic and this same transmission routes power to all four wheels, transforming the big luxury sedan into a serious snow vehicle. The Mercedes S63 AMG has a 6.2-liter V8 capable of 518 hp and 465 lb-ft of torque. The S63 also uses the seven-speed automatic, but it's recalibrated for faster, firmer shifts. Since this is an all-new Benz, the latest advances in safety equipment have been incorporated. Stability control, eight airbags (including side window curtain airbags) and brake assist (which automatically applies full power braking if it senses a panic stop situation) are all onboard. So is Mercedes' Pre-Safe system, a useful bit of technology that can sense an impending crash and automatically tighten up the seatbelts and reposition the power seats for maximum airbag protection. Interior Design and Special Features Mercedes' COMAND (Cockpit Management and Data) system is much easier to use than before, as there is a larger screen mounted to the right of the instruments and many controls are redundant. The only ergonomic flaw is the turn signal stalk, which is located somewhat awkwardly down low and away from the driver. Simple elegance marks the cabin decor, with high-quality materials, richly polished woods and soft leather all around. The optional Dynamic Multicontour seats have 11 air chambers that essentially allow you to mold the seat to your body. During aggressive driving the side bolsters automatically pump up and down in response to cornering forces, to better hold you in place. These seats can also provide a soothing back massage. Another interesting feature is the optional Night View Assist system. Unlike thermal (heat-sensing) systems, this one uses infrared beams to provide sharper images and light up inanimate objects that don't give off heat.