Some cars you buy for looks, some for comfort, and some you buy not because you will ever know their true capabilities but for the bragging rights to what it "could do." Of course bragging rights can come in several forms, top-speed, 0-60, lap-times, etc... So which car would you choose just to be the baddest in the land? Would you choose something from the factory, or would you have the tuners do their work?
For me the answer is simple. I'd pick the E63 AMG S 4matic wagon, RS6 Avant not available in the US :(. I could brag that I can carry my family in comfort, not attract the unwanted attention of the 5.0, but still have the goods to run with the best of them.