I have an Aria and you can BARELY hear the PS fan. If you couple that with a G3 cpu card and gfx card with no fan, you have a nearly silent machine. Really, the rear 120mm fan spins very slow (yet pushes alot of air) and is near-silent. Can't really beat that....unless you can find a compatible external PS like those on the A1200 and A500....if you do let me know :)
HammerD
A4000/060/PPC-200MHz, A4000T/060/PPC-233MHz, CD32, MicroA1, Pegasos 2 G4, AMD Phenom Quad Core 2.5GHz, MacMini 1.5GHz/64MB VRam...mwwmwahhh :)