The current gen M3 is the biggest car I ever want to own for myself. In fact, I still find it a bit too large (and heavy). My next car will definitely be something smaller and lighter. I wouldn't take an M6 even if it was a straight up even trade with my M3.
(1:40 @ Laguna Seca, 2:03 @ Thunderhill, 1:52 @ Infineon)