M6 and m3!
The M2, my fav. God that car looks great.
Tough to tell but it looks like the m2 has a little more neg camber in the front and a little less in the rear than the m4... might help contribute to what the reviews are saying about the front end biting harder/more nimble feel... of course the shorter wheelbase helps quite a bit.
I highly doubt the cooling on the top of the n55 weighs a hell of a lot, or would noticeably change the feel of the front end.
Want want want!