Hey Rob, sorry to hear about the accident. Sounds like you are okay so thats the important thing.
I hope you find a suitable replacement! There is always the used option. The C63 is certainly a beast if you want to buy new and stick to a 4 door. I know its more expensive but have you driven the M5 or even the 6er Gran Coupe?
I am with you on considering something else other than an E92 M3 with having had two E90 M3's already.
Let us know what you decide