>> the 2.5 is the second fastest G5 currently supported.

> What would be considered the fastest. But also compatible.

http://www.everymac.com/systems/apple/powermac_g5/specs/powermac_g5_2.7_dp.html

> I'm a little confused by the compatibility list.

Why? It says that "Only PowerMac 7,2 and PowerMac7,3 (A1047) are supported", which shouldn't be confusing at all.