XFX GTX260 power consumption

it must be a typo cause the 260 only requires like a 500 watt psu

But then again, the GTX 285 supposedly requires a 550 watt minimum power supply, but also requires 46A on the 12v rail. A bit of simple math equates that to 552 watts, so this magical card manages to feed itself power

Well by good I meant good Brand. For efficiency, 80+ for sure is preferable, however this has no effect on performance of the PSU (except for more heat). The rated power is the DC out, not the AC in. (500W @ 0.7 efficiency = 150W waste heat, 500W @ 85% = 75W waste heat)

No, the 550W is after the efficiency loss. in other words, (at 70% efficiency) 650W comes into your PSU, 150W comes out as heat, and 500W goes into components as DC Power. The quality aspect is really asking, did the manufacturer do max continuous power or just max power, and can this PSU really output at that at all.

Regardless. To answer your question, you should be fine. I almost could run a 2900XT on a mediocre/poor 550W, so you should be fine.

It all depends on your system specs, how much +12V the PSU can deliver, and whether you plan to OC . There's a big difference between a stock e8400 and an OC'ed core i7. Add multiple drives, etc., your requirement could go way up. So how "loaded" a system make all the difference. Really can't answer your question without knowing:

What are your system specs?
What PSU are you talking about?
Will you OC?

Oh, I'd say that's asking for trouble.

That PSU doesn't list a max +12V, but the best it will be is 32A 12V. Way too little for 4.0GHz i7 and a GTX285.

Personally, I'd even be leery of a quality 550W with those specs. Something like the Corsair 650TX would be my PSU choice for that system: http://www.newegg.com/Product/Prod [...] sair%20650