Nihilation

I'm looking at a set of 18x9.5 et22's locally and wondering what they'll look like on my 535i (with sport pack) and what is the widest tire I can run that will fit under the front fenders without rubbing. Ideally I'd have a square setup so that I can rotate the wheels to extend tire life. I don't mind running a spacer if needed to get it fit right. Any input is much appreciated.