How much wattage does this build need?

[TheGamerCatHD]

The build I'm asking about is

Cpu:Intel Core i7-4770K 3.5GHz Quad-Core
Cpu Cooler:Corsair H100i 77.0 CFM Liquid
Motherboard:Gigabyte G1.SNIPER Z5S ATX LGA1150
RAM:Corsair Vengeance 16GB (4 x 4GB) DDR3-1600
HDD and SSD:Western Digital Green 2TB 2.5" 5900RPM
GPUS:MSI GeForce GTX 770 2GB X2
Case:NZXT Phantom ATX Full Tower
DVD Drive:Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer
Moniter:BenQ GW2750HM 27.0"
Wi-FI Card:Asus PCE-N53 802.11a/b/g/n PCI-Express x1
Case Fans: Corsair Air Series AF120 Performance Edition (2-Pack) 63.5 CFM 120mm

Thinking of use the Corsair Gaming 800W 80+ Bronze Certified ATX Power Supply

Thanks

Edit:Would it be better to get one 780 or two 770

 

[3Dns]

600-650 is good enough and safe. Your system need 400-450 but take 600+ to be sure

If you looking for a cheap one and good take this http://pcpartpicker.com/part/evga-power-supply-100b10600kr
Here is a decent choice http://pcpartpicker.com/part/evga-power-supply-100b10600kr
And here is the perfect choice http://pcpartpicker.com/part/evga-power-supply-120pg0650gr

 

[nostall]

Looks like a pretty nice build
Regarding power. Nvidia recommends a minimum psu of 850 watts for the entire system with a minimum of 62 amps on the 12V rail. The total wattage is not the important concern, but the amount of current measured in amperes that the PSU can produce at 50C.
That PSU specifications show that it can produce 66amps. on the 12v rail and should be sufficient for a normal system without any OVERCLOCKING. Overclocking increases the need for more current, and rather quickly.
That said, your processor and video cards beg to have some overclocking done on them; with that in mind I would step up to an 850 watt HX or 860watt AX Corsair. The HX or AX have longer warranties.
If budget is an issue (and it should Not be when considering the PSU-if the psu goes bad it can destroy your very costly excellent parts) then do a little shopping for an 850-950 unit by XFX, Seasonic, EVGA SuperNova, Antec (some killer sales on antec right now).
Here's a couple good sites to look at reviews of PSU's you might consider:
http://www.jonnyguru.com/modules.php?name=Search
http://www.hardocp.com/