That psu should be sufficient (it has enough watts and amperage for your setup), but it could be plain old faulty, that's why I suggest trying another psu to see if another comparable psu solves the problem. Is it new?
Also, are you monitoring your temperatures? Make sure your cpu or gpu isn't overheating and causing a shutdown when you don't expect it. If your gpu fan or H100i pump isn't working properly you could be overheating without even knowing it and your pc may be shutting down to protect you.
Asus RIVBE • i7 4930K @ 4.7ghz • 8gb Corsair Dominator Platinum 2133 CL8
2xSLI EVGA GTX 770 SC • Creative X-Fi Titanium • 2x 840 SSD + 1TB Seagate Hybrid
EVGA Supernova 1300W• Asus VG278H & nVidia 3d Vision
Phanteks Enthoo Primo w/ custom watercooling:
XSPC Raystorm (cpu & gpu), XSPC Photon 170, Swiftech D5 vario
Alphacool Monsta 360mm +6x NB e-loop, XT45 360mm +6x Corsair SP120