I have ALWAYS known that the E39 BMW M5 is the fastest production sedan in the world.
Brabus simply tunes Mercedes, that's a bunch of crap.
If it isn't the M5, it's the Lancer EVO (but I doubt it). Not the E55 AMG, though.
The new Audi S6's coming out and it will be the fastest when it comes out (waaah, M5's gonna lose)...