Why? If I were you I'd sell that G5 rig and upgrade the memory in your Mini.
Agreed. The G5 is a pretty old chip at this point, and not being able to run Snow Leopard will make you sad very soon.
Core i7 920, 3x2GB Corsair DDR3 1600, 80GB X25-M, 1TB WD Caviar Black, MSI X58 Pro-E, Radeon 4890, Cooler Master iGreen 600, Antec P183, opticals