As far as I know, G4s are way louder than G5s... Which is something important to consider, but, as G5 are not yet supported...
Any information about silent g4 models?
My 933 quicksilver is really loud.
My watercooled G5 @ 2.7 GHz is freakin' loud under load. I swear something's wrong with it, but I tore it apart a few times and see no leaks. If they ever support a G5, stay away from the higher end models that are watercooled. The air cooled 1.8 and 2.0 are silent.