You get what you pay for with pumps. I would recommend the March or Chugger pump with a stainless head. Shop around for prices. Don't assume that places like More Beer have the best price. There are many other resellers that are less expensive, especially on the Chugger pumps (remember to calculate shipping into the price too).
I have a single tier system with two pumps. I just replaced my March pumps with Chugger pumps. The Chuggers are much quieter and seem to be a little faster, but that could just be my imagination. You won't regret getting a pump since it will make your brew day so much easier.