From the guys at Autoblog

There was a time when what we might call super-sedans were largely the province of a dedicated cadre of aftermarket tuners. Companies like Brabus, Alpina and, of course, AMG would generally start with mid-sized German sedans and transform them into something truly special. AMG in particular came to the forefront in 1987 after two decades of building special Mercs when they unleashed the Hammer. They had been building cars for two decades already, but the Hammer took things to a new level by installing a 5.6L V8 from the 560SEC coupe modified with twin-cam four valve heads into the mid-size 300E sedan. With that car, AMG set off an arms race that continues to this day. The tuners are still out there but AMG was eventually brought in from the cold when it was bought by Mercedes-Benz. Today AMG produces high performance versions of almost all Mercedes models and standing near the pinnacle of the lineup is the S63 sedan.

YouTube - Autoblog drives the 2008 Mercedes Benz AMG S63

The S63 is not quite the ultimate S-Class from Mercedes. That crown falls to the twin-turbo V12 S65. The S63 is instead powered by AMG's bespoke 6.2L naturally aspirated V8. AMG designed and built this exclusive V8 that is installed across the range of AMG badged models. Unlike previous AMG engines, this one shares no parts with standard Mercedes engines. In the S63 it generates 518 horsepower and 465 lb-ft of torque, enough to propel the 17-foot long, 4665-lb S63 to 60 mph in 4.5 seconds and achieve an electronically limited top speed of 155 mph. Opting for the $7,000 performance package adds a 20-inch wheel/tire package, a limited slip differential and a reprogrammed speed limiter set to 186 mph. You might be asking yourself, what possible good is that extra 31 mph in the United States where there is nowhere to legally use it?

While super sedans are more elevated than ever, the effect on their performance is seeing diminishing returns as manufacturers try to outdo themselves with technological wizardry. This is where the S63 truly shines. Unfortunately, in some respects it is also its downfall. There are almost no features available on any high end car anywhere in the world that you won't find on the S63 and there are also gimmicks in this car that can't be found anywhere else. We don't use the word gimmick lightly here. While there are useful features like adaptive cruise control, others are absolutely superfluous. Top of the list here is the Drive-Dynamic front seats, which surprised when taking the S63 around our first corner. As the car builds cornering force, the seat bolsters begin to grope your sides. As you turn left the right side bolsters push inward, presumably to hold you in place. Turn right and the opposite side moves. This is a feature that adds weight and complexity to the car without adding useful functionality.