03-18-2011, 09:46 PM
G5 2.5GHz DP liquid cooled was pretty noisy. G5 2.3GHz DC was almost silent. Several MDD G4's also varied in fan/noise level. One QS G4 very loud, other kinda noisy but bearable until rebuilt under AppleCare... then worked better than ever; totally awesome, but morphed into loudest of all. Vast PPC tower experience shows it's the luck of the draw. As noted, keeping them clean helps, as does being careful w/ how cables and other interior stuff are routed in relation to the fans. It's far from an exact science.