Last series of the G5 PowerMacs (11,2) are air cooled with PCIe, and is my preferred G5 beast. I picked up a Dual Core 2.0 (http://www.everymac.com/systems/apple/powermac_g5/specs/powermac_g5_dual_2.0.html) cheap, and it is doing most of what I used to do on my venerable QS2002, except of course when I those rare occasions I need to boot 9.2 or use 10.4+Classic with more grunt than the Cube450, or iMac800 can provide.

The dual 2.7 was only available in the liquid cooled PCI-X varity.