Since price is the #1 concern, IMO, you can't go wrong with bimmerbrakes. Not only is the price good, but the service is great and you are basically buying stoptech parts without the stoptech price. Why pay extra when you can get the same stuff for cheaper.
My rear brakes are about to go and I've been talking to Anthony@Bimmerbrakes and he is a stand up guy. Answers all the dumb questions I have and is always prompt. I have also hear nothing but good things about him from several people I know.