I posted this below, but just incase no one scrolls down that far, here's some more information on the Dinan SC debate.
I just had a ride in this guy's Dinan SCed Mcoupe and damn was it fast! I know the Mcoupe is faster than the M3 to begin with, but, it also has the same 3.2 liter engine as the 96+ M3s (I was told that the SC was identical to the one for the OBDII M3s...construction, HP gains, etc.). Anyway, he recently got his car dynoed at Competition BMW in CT and from the rear wheels, his output was 315HP. I didnt get the figures on the torque measurements, but that was the correct figure and he does have the papers to back it up. Im not sure if comparing the HP gains between the 2 cars is a fair assessment, but since the engine and SC is the same, i would imagine the HP gains would be too????