I have yet to see a quality psu that comes with enough PCIE connectots, its annnoying.
The Corsair AX750 is probably the best PSU out there, but also probably overkill for your needs, but if you want the best, that's something to look at. [..] Thermaltake Toughpower Grand GOld 750 also good and going for cheap.
Those are just some of what's out there, but they're all quality units with good warranties in case you get the rare defective unit and they're not bank breaking (I recommend gold rated PSUs for anyone running a 24/7 high load rig, as it will actually pay off the price difference in a reasonable period of time).
whenever you have PSU questions, etc or are considering a new build,
http://www.extreme.outervision.com/psucalculator.jspI also use
http://whirlpool.net.au/wiki/psu_recommendations, but, yes, 1250w should cover most sins
750w will probably not be enough to cover GPU + CPU at peak, as the general peak load looks like 769w, and 1100VA on AMD 940, 741w/1060VA on i7 2600k
but the big issue is the 12v capacity, will need to be over 58-60A to handle the PCIE load on those cards. that's what to check for.
you should aim for 850w silver/gold or 1200w bronze/silver if you want more reliability or need specific cabling.
in some places, 1200w is cheaper than 850w silver rated PSUs, but, ultimately, brand names charge more. i.e. seasonic X series = Corsair AX series, same seasonic hardware, $50 difference.
as for the bronze/silver/gold, the 80+ gold rating applies to PSU conversion efficiency, soo, if you run the PSU at half-load capacity, i.e. 300w peak load on the big sticker 750w PSU , it will use less power and cost $50-100 more than the equivalent 750w. you're pulling ~740-780w, 60-63% of 1250w, so aim for the 1200w series on a cheaper PSU, or get a modular 850w-900w PSU, both should cover the same power load and the 12v rail
that said, silver rated at 50% load, will be roughly as good as a gold rated at 85% load. that gold standard is pretty damn good. i've run a 6970 x 2 on 750w gold for 3 days, no issues, and that was somewhere around 88-90% load.
Whenever you have PSU questions, the last thing you should ever do is consult an online PSU calculator. outervision is good, but not that good.
What you should do is find what a card actually draws as I did and plan accordingly. 750Watts is beyond enough, arching on to overkill territory. Wall power draw is not the same as system power delivery, that's what efficiency relates to. These are 6870s not 6970s
If you can find a *quality* 1200W for cheaper than a *quality* 750W, and come up with the same efficiency then by all means go ahead, but I've not seen that math work out very often. I don't know of any 1200W PSU that retails under $200, while you can find plenty of gold rated 750W PSUs for nearer $100 than $200. But feel free to shop around.