I currently run an Nvidia Quadro 4000 which works well with Premiere but is not working well with my 3D software. I really need something that will work well with both programs and ideally be powered from the Mac Pro's PSU. Can the GTX 580 do this or does it need to be run from an external PSU? Is the GTX 680 better still? Do they have to be flashed with some Mac guru's code to work on a Mac? GPU's for Macs seem like a black art now so any help would be hugely appreciated.