The G5 power supply is more than enough for 2 cold cathodes. However, there is only one molex power connecter, and that is on the superdrive. You will need to purchse a splitter for that. I have done this on a Rev A. 1.6ghtz G5 so I know it will work. Also, be sure you run cables well, as you don't want to spoil the look of your G5 by having cables sticking out.
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Mobile-2.2Ghtz Core 2 Macbook, 4GB ram, 160GB HDD
Server-Dual 1.42 MDD G4, 1GB ram, 4 random hard drives.
PC-C2D 2.4Ghtz, Asus Commando, 2Gb ram, 3 hdd's in raid 5, 8800GTS.