I own both, 01 M5, 00 GTS, the Viper will kill the M5 anytime. I love my M5, different car for different purpose. The Viper is a pure race car that can be driven on the street. Rwhp dyno around 400-420 bone stock with significantly less weight than M5. M5 still "the baddest sedan on the planet." Interesting thread going on at viperclub.org in off topic section, with arguments among us Viper owners who have M5's as daily drivers vs. other Viper owners with E55, S4, Lexus models, etc You now what side I'm on, come on over and help me out! S4 indeed! Lexus?!