The difference between running a radiator with NO fan, and running one with say a 69cfm 120mm at 7v (about 40cfm) is AMAZING. If you were to take say, the thin 120mm 69cfm fan they sell at CaseEtc, which is already under 30db (like 24 if I remember right) and run it at 7v, it would not make a sound. That's what I think you should do.