My Trek 1500 came with generic brakes and I have not been too happy with their performance. They have little progressive response, have mediocre stopping power, and the pads spray black graphite (?) over everything. I want to replace them, and the two choices I've cme up with in my price range are: a) Shimano Ultegra BR-6600 b) SRAM Rival I already run some Ultegra on the bike (rear derailleur, pedals), so should I stick to Shimano? Don't know SRAM, but hear more and more in mags, etc. Any pointers from the mechanically-minded out there? Actually, while I'm here, perhaps I can ask one more question. The Trek 1500 is an alluminum frame mid entry-level bike with low-end Bontrager triple drive train ($1400 Canadian). Is it worth upgrading the drive train to a mid-level Shimano (Ultegra) double (perhaps a compact?), or would it be best to save my money, ride this machine for a year and then buy a new bike?