imo. EVO and STI if your into that.
but C63 have alot of potential, they also have tunes that add 70-80 HP. Most amgs actually. E55/63 with intake pulley exhaust can run 11's.
B5 S4's can be very quick. You can also go into muscle cars. Thats where the fun starts. intake header exhaust tune can add a good 50 Hp. superchargers add alot of power. personally, id get an evo. full interior buschur powered evo
9 seconds all day