Go to the Tires Plus on 2607 Gulf to Bay. Basically in the new Clearwater mall. I went there with the same intentions, with the idea of paying the full price, but the manager took me out to their tech, told me to give him $40 cash, and he'll balance/mount all four tires.

Its basically $10 a rim, and takes like 15 minutes. Go in the afternoon, when they won't have too many customers.

I wish I could tell you their names, but I don't recall. Ask if they can do the same deal for you...

Edit: I ordered the Tires from Tire Rack. They didn't care where you got them from.