Enough is never enough, at least for the power-mongers who toil at AMG, the performance division of Mercedes-Benz. Brilliant engineers who infuse mainstream Mercedes products with extraordinary performance capabilities, the wizards at AMG are fiddling with the S-Class - again - for its final year on the market before an all-new replacement arrives for 2007.

Whether the installation of a hand-built, 604-horsepower, 6.0-liter, twin-turbocharged V12 engine that generates an astounding 738 lb.-ft. of torque qualifies as fiddling is a subjective judgment. Irrefutably, however, the resulting Mercedes-Benz S65 AMG thunders down the road, surpassing 60 mph in 4.2 seconds on the way to an electronically limited top speed of 155 mph.

Power flows to the rear wheels through a five-speed automatic transmission equipped with SpeedShift manual controls. Bigger, internally ventilated and cross-drilled brakes with fixed eight-piston front calipers; larger, staggered-size AMG twin-spoke alloy wheels with performance-grade rubber; and suspension tweaks accompany the massive infusion of horsepower and torque. The standard Active Body Control (ABC) is calibrated specifically for the S65 AMG, and the steering is more responsive for greater precision. Stability control and brake assist are an integral part of the package to ensure that even the most talented drivers don't get in too far over their heads.