I remember writing about these cars but don't think they had their own thread. I drove all of these cars during Car and Driver's 10Best a couple years ago.
Anyway's, here's the summary 
M3: Unless you're driving it on the track it's not all that special on the road. What's amazing is that if you test drive an E36 with a manual trans today it's still a fun car and that motor is a gem, even without the individual throttle bodies. Don't believe what the mag's say and most of us won't be taking these cars on the track anyways.
C63: You don't need a track to appreciate what this car can do. The sound is unbelievable, the motor is one of the best, handling is on par with the M3 and light year's ahead of the C55. The interior is in another league compared to the M3 and the seats are phenomenal.
A4 3.2: Don't even bother to drive this thing...just go with the 2.0T and never look back. My bro has the new 2.0T and it's a lot of fun to drive, even with a slush box. The engine is torquey and very responsive.
