if you want quiet power supplies look for Engelking. Yes, they are pricey as hell, but they come in many variations, even completely without a fan and half-height (where you should mount a passive cooler or a waterblock!!! on one of the surfaces to remove the heat). They seem quite low regarding their watt ratings, but believe me, these figures are strongly below what these babies are capable of. Generally you can multiply their figures 1,5 to 2,0 and you get the Enermax-rating
For silent computing nothing beats watercooling though. I managed to run my overclocked 1800+ with an overclocked GF3 on passive cooling and remained below 60°celsius while under full load (i.e. gaming, Morrowind). The loudest thing in my current setup are my harddrives, even the keyboard I´m typing on makes more noise than my pc. Just make sure to get a high-quality silent pump (I recommend Eheim, a 1046 is sufficient for CPU,GPU,Northbridge and a huge radiator).