everythings already been said this question was answered good. but one suggestion when you pull power from a pc power supply, dont cut and splice it. get some of those disk drive power connector y splitters and splice into those.
That way the first time and on down the line that you have to replace the power supply, its still just a plug in deal, theirs no wires to splice, youve already done it with the disk drive splitters. pull the old one out, plug the new one in.