I'm picky about what tires i run on my Audi S4 both for performance and safety. i was referred to Tires, Inc. by THE car expert in Boulder, Frank Amoroso, and i have not been disappointed. I find the staff at Tires, Inc. to be knowledgeable, helpful, patient and friendly. They'll work with you to find the right tires for your specific needs and car -- not just sell you crappy tires at the lowest price and send you on your way. They found problems with the mounting and hardware on my car when Discount Tires had put on a set of custom rims i ordered. They also offer wheel and tire storage for your winter set (you should have a separate set of winter tires people!).
I recommend them highly.