I also have an iMac, and loved the silence. I got a dual 1.25 G4 (FW800, not the ones they're selling now) a few months back, and its considerably louder than the iMac. I used to leave the iMac on all night, but I have to put the G4 to sleep at night because it literally wakes me up in the middle of the night from the constant drone. And this model is supposedly one of the "fixed, quieter ones". I don't know, it's an acceptable level of noise, certainly on par or quieter than a high-end Pentium 4. If noise is a serious concern though, I'd think twice about getting a Power Mac G4, unless you want to drop $300 on a
Verax fan kit.