I have been seriously considering buying a c63 most likely an 09 or 10. So the past few months I've been looking over the mb forum. Today I found this thread about a guy who converted his c63 into a black series and what an awesome job he did.
Dads C63 BS Sedan Conversion - Page 10 - MBWorld.org Forums

I have also noticed that the guys on the mb forum don't seem to go real crazy with mods. I get the feeling that they do not have the connection with their cars like most of us on here do with our crossies. I guess when a car is still being produced the thought that this might be the only one you get to experience doesn't cross your mind.