I am going to have to agree with going with 18s. I currently have 19s on my coupe (bought that way), but keep finding myself wishing that I had 18s instead. I have changed a few tires that had nothing to do with wear and tear...potholes and bad roads are certainly not your friend. As for performance, its hard to tell for me as I am not sure how the car performs with stock wheels. I can tell, though, it is a bit sluggish in the "get-up-and-go", but when it gets going, its haulin'. Better have the right brakes/rotors to stop it as well. Oh, and the steering wheel, I think, feels heavier as well. I have had older BMWs with "heavy steering", but this is the worst!
PS - I dont think I have experienced any rubbing with mine though!
"sim simma, who gat di keys to mi bimma" - beenie man