While no fan isn't the best course of action, a quality supply that is not overloaded is adequately cooled by a single 80mm fan of modest spin rate. Something in the 27-32cfm range is fine, and nearly silent if the fan is quality. I recommend the Panaflo units if silence is the goal, but any quality unit will suffice. Often sleeve bearing fans are quieter than their ball bearing counterparts, and have proven just as reliable in my experience (they all work until they fail...). The idea of multiple fans is a gimmick designed to seperate one from his hard-earned cash. Bigger fans, such as a 92mm (or in the lovely new Fortrons with 120mm fans) will allow lower noise levels yet, but an 80mm will do in a pinch. Multiple fans just raise the noise level, as they have to exit through the same 80mm exit fan they can do little to improve ventilation.