I've found that Basanni makes high quality stuff, but have never looked into exhaust for my 5.
I'm gueesing you'll hear recommendations for Dynan or AC Schnizter stuff. I guess I'm just rambling since I really don't know anything useful.
2002 BMW 530i
1997 Ford Mustang GT
1995 Honda VFR 750 (For Sale)
1964.5 Ford Mustang