If you are considering getting a gyre, then this may be your solution to your circ pump issue. Choff was mentioning running his gyre (and loving the circulation it provided) and discussed shutting down a couple of his rear pumps. I wouldn't want to shut all 4 down because I believe you need some circulation back there, but 2 pumps running would work. This will allow you to toss the bad one and have a spare in case another fails.