Its probably been said over and over in this thread: CTS-V
2008+ M3 sedan, a real back seat, 414 hp V8 revs to 8200 rpm, handles great, fast and you can get it with a real 6 spd manual. Great daily driver/track car. You cant fit people in the back seat of a GTR, i've had 911's and only kids fit in back.
I'd say C63 - incredible engine, power oversteer on demand, great steering, glorious V8 soundtrack, similar level of performance to a F430, seats four comfortably.