Maybe the cheapest and easiest solution is to sell the G5 and buy a Mac Pro in its place. I'm fairly confident that the heat output from the newer Mac Pros is much less than the G5s. The liquid cooled G5s have a high rate of failure due to the cooling systems leaking, but in some cases Apple has been replacing those failed units with Mac Pros.

Jasen: The solution to eliminating condensation might be to vacuum seal the G5 inside of an airtight material like mylar or plastic. Eliminating the air would also eliminate any moisture and prevent condensation and ice crystals from forming. It would probably also wreck the CPU since there would be no air to help transfer heat away from the heat sinking.

Is liquid nitrogen not a realistic alternative? XD

dry ice would be better, easier to handle and still -80oC.

...and would you expect better performance once the chips were super-cooled?? ;-)

I'd expect them to crack, then fail.
;)

I remember the days when I had a noisy G4 tower, then bought an ibook. the peace and quiet was worth the drop in power. I saw no reason to ever buy a desktop again and haven't!