The only difference between Sora and STI shifters for that 7 speed would be that you can't "trim" the front derailleur on the Sora. The Sora "brifters" will also only jump two gears in the rear instead of three. I keep my bike nice and clean, and the Sora shifters work as well as the Ultegra shifters on my other bike. I put new wheels on my older Trek 420, and they had to put a spacer on the hub for the 7 speed cassette. Maybe you should go to a good LBS and ask them these questions. They can measure the dropouts and tell you for sure. When I put a new cassette on the back, the shop used an 8 speed chain for the 7 speed cassette. They said a 9 speed chain was too thin for the gear teeth. I found the 7 speed Sora shifters on Sheldon Brown's Harris Cyclery web site.