if u want a quiet computer without getting into watercooling, i wouldn't put in ANY case fans except one in the psu.
also, i've read numerous people buying 1.33ghz t-birds and under-clocking/volting them to 1ghz and passively cooling them...(just large copper heatsinks w/ no fans)...
also, consider video cards like a Radeon LE or similar that run relatively cool without fans...MXs can do it too...other "higher" end models can as well if u use your own larger heatsink
monitor your cpu/case temperature w/ and w/out an exhaust and intake...i've noticed that an intake doesn't do much for cpu temps. while an exhaust does...it can take off ~5 celcius off the peak temp, but that's not a big deal if your cpu temp. is already well within it's max. tolerance.
finally, if u don't wanna buy a new psu, it's easy to hook up your own 80mm fan to it...
oh, if u see any of those 12v snail shaped fans, they're extremely quiet and can be good exhaust fans...actually, even good cpu fans if u can find a decent way of mounting it....