For me the problem with the C63 is the cheap plasticy feel of the dash and more importantly the lack of exciting color options for the exterior and interior. Pretty much all the C63s that you see out there are Silver, white, or Black with Black leather. BORING!
I just searched ebay motors and almost all of the C63 AMGs are just as I said.
Check it out for yourself:
Yes the engine maybe a torque monster but IMO, if you want the balance of engine, performance, handling, style, and support from the enthusiast community then the M3 is the only way to go.