kaninjaHCP1200 is the way to go.

More like overkill. This would be my suggestion.

http://www.newegg.com/Pro...x?Item=N82E16817703022

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I'd like to add my input on "Single or multi rail?".

It's been explained on the first page that multiple rails are usually just one big output divided into smaller outputs, but things don't stop there. People who are obsessed with single usually think a 100A single rail is huge and powerful, unlike a 5x20A multi rail which is (in their opinion), weak and resetting, or say, POS or BS. In reality, it's not. Because these multiple rails are so powerful you can never shut them down. I find the SilverStone Strider 1200 suitable to make an explanation on this subject. So let's have a look.

"SST-ST1200
Max. DC Output
1200W
Load Range
 
+3.3V +5V +12V1 +12V2 +12V3 +12V4 +12V5 +12V6 -12V +5VSB Max.(Amps)

40A     40A      28A     28A     20A      20A      20A      28A     0.8A    6A"

As you can see, this is a 6 railed PSU. The first, second and the sixth rail (28A rails) power each GPU. (meaning this PSU Tri-SLi capable) Those 3 rails then combine internally on the shunt point to turn into one big 60A rail. Using the Amps to Watts calculator here

we can find out 60A equals to 720W at +12V. This however is just the combined number, the OCP set-point (point of shutdown) is usually set even higher. I assume about 800W+ for this unit. Now, each GTX 580 pulls significantly lower power than the other. Therefore, we don't just add up 250W after 250W. It goes like 250W + 200W (depending on scalability) + 200W. To round up, stock Tri-SLi 580's would pull about 650W in games. FurMark for example loads cards up a lot more. We can also assume full system power consumption by adding in the rest of the parts.

Coming back on the CPU rail... the Strider 1200 has two 20A rails for your CPU, and that makes it 240x2=480W+. The TDP of an i7 920 is 130W, so even with an OC, you can never pull that much power. Last but not the least, there's this peripheral rail. We have a 20A=240W+ for it. Since your HDD's, fans etc. would never need 240W+ under normal conditions, you can't shut the unit down from there either.

Moral of the story: Multi rail WILL power your system without issues, and when it does, it'll do it safer by dividing the load. I hope this clears up the misinfo on the first page.