I'm in the process of creating the most extreme and VOIDED of your warranty mac. It's a Dual G4 500, OC'd to 600. If I weren't limited by the crap offboard L2 cache, i could easily reach 700+. My guess at what the temps will be is -10 degrees or less at idle, and stil well under 0 degrees under full load, as my old intel p3 was putting out near 50 watts of heat, cooled by an 80 watt TEC. The dual G4's will be cooled by 2 80 watt TEC's. I have a few pics so far...I'm going to release the article in a few weeks. Tell me what you think! Currently, i'm waiting on a new PSU that will power the 3 TEC's, and a 2 copper plates to clamp the waterblock/peltier to my geforce3.