I drive an '01 325xi, right now I just have stock 16's with siiiick nokian runflats. Probably next spring I want to upgrade to better performance wheels. Can anyone tell me if my car is compatible with say m3 or m5 contours. I think 17's are the biggest I should go. Any input appreciated...

M3 Contours should fit fine. You might have offset issues and need to run unconvential sized tires with M5 wheels.

IMHO M68 wheels look great on any E46