Or the other way is to grab 4 pin molex power from the optical and use the adaptors usually supplied with a PC card. Some people make their own.
Roms
I have one Mac 285 and one PC 285 and the ROM chips are very different and the files a different size. Watch out for posts by people like Rominator - there will probably be a growing list of flashable PC cards noted in the coming weeks. It is a bit early to so this - my best guess is that a PC EVGA card has highest probability of working.
Unless you absolutely must have a card that starts right from boot netkas' injector is very good for PC 285s - it is loading my second GPU. It is not 100% effective - some people have it working, others not. I suspect this will improve as netkas figures out more parameter settings.
Added in edit: I would now say that you should not even think of flashing until the Mac power management is sorted out.