okay, everyone says 1000W is overkill for a single gtx 280 system (not sure if this is true, so that's what i'm asking sort of) but anandtech says 1200 (1000 not enough) for sli'd 280's, so that 1000W really doesn't make any sense for me any more. what i'm wondering is if i can get the build going with a 750 pc&p then?
the also said the actual usage in real life was lower than 225 watts for a single card...I don't remember the exact number. You should be fine with a 750 and 1 card, and probably 2, but that's cutting it close considering add ons and oc'ing.
The Anandtech review actually says:
"All of the power supplies on the GTX 280 SLI certified list are at least 1200W units."
They're just mentioning that the list over @ http://www.slizone.com/object/slizone_build_psu.html showed only 1200w units as Certified.
I think that list is being updated over time since there are a couple 1000w units on the list now.
I calculated how much wattage a very high-end PC would take (note that these are some of the worst-case scenario wattages, and that the wattage would only be at these numbers if the parts were at pretty much their absolute highest power usage, which almost never happens):
Motherboard - 50 watts
CPU - 150w (for a high-end Intel Core 2 Extreme Quad, not super-overclocked, maybe about 3.2 GHz, but at maximum load)
RAM - 50w (for five sticks)
2 GTX 280's in SLI - 474w
Five power-efficient hard drives, or a smaller number of less-power-efficient ones - 50w
Sound card - (I'm guessing, but no more than 15w)
2 optical drives at full power - 60w
Miscellaneous (fans, lights, etc.) - 30w
Which comes out to be 879 watts, and typical usage would be much less, especially if not gaming, since the GTX 200 series cards have built-in power-reduction for when idle.
But, like is often said, watts don't mean squat! Or in other words, total wattage isn't everything for a PSU. It is likely that some 1000+ watt PSU's can't run 2 GTX 280's in SLI because of amperage/wattage requirements on the 12v rail(s) alone. NVidia's recommendation is to have at least 40 amps altogether on the 12v rail(s), and at least 550w total wattage for the PSU.
Also, I heard that some PSU's can't distribute their power evenly to multiple 12v rails when using high-power video cards. If you're looking for a reliable brand, PC Power & Cooling is the way to go. Their 750w models have a single, 60 amp 12v rail, which is plenty for most gaming systems, and 825 peak wattage. This could probably handle the system I mentioned above, as long as the user doesn't max out every part at the same time.