For most automotive tasks the Viper is overkill, like using a six-pound sledgehammer to swat a fly. Ridiculously fast and able to slosh your eyeballs about in their orbit rounding a bend or under heavy braking, it didn't really need any more power. But with archrival Corvette Z06 at 505 hp, that's just what Dodge did for 2008. They made the engine just 0.1 liter bigger but added 95 horses to make a nice round 600. The fly would still be dead, but now you have a bigger hammer.
Along with the increased power, the gearbox has been strengthened, the shifter revised, the clutch tweaked for more grip on less effort, and the hood has been reshaped. Almost irrelevant are addenda like a navigation radio.