So long story short, I wanted to build my own rig last year, but an emergency came up and I had to get a pre-built at a local retailer ASAP. It was at a great price, and I only needed to use my GPU that was still fonctional from my old computer (GTS 250). Fast forward a year later, I'm finally done school so a GPU upgrade is in order.
Now I don't plan to OC or Sli (well, not with that PSU and my mobo anyways)... but my question is: Am I risking damage or performance issues if I don't switch out my PSU for my new GPU? Or am I still "okay" as long as I only use a single GPU?
Here are the other components (not home right now so the details might be off):
-Intel 3570k (stock clock with stock fan)
-Kingston 1333mhz (8gb)
-Sandisk Extreme 1 240gig
-500gb HDD Seagate
-Rosewill Redbone U3 (with stock cooling)
-LG DVD drive
The GTX 770/760 are only going to need 500-550 watts maximum. From what I gather from that review, you need to avoid pushing that PSU really hard, over 600 watts worth of usage. So, I think you'll be alright since you have plenty of overhead and don't plan to OC.
In any event, I doubt your setup's going to suddenly explode on you the first time you hit the power button. I think you'll have the opportunity to play with it a while and see just how bad that PSU sucks before you decide you need to replace it.
The thing to look for is how many amps the the GTX 760 or 770 uses on the 12V rail on your PSU. Since your PSU supports a maximum of 56A then you should be ok. Another thing to note is that other components will draw from the 12V rail also, so you want to make sure you dont overdraw on the Amps. Check the NVIDIA site to see how many Amps those cards use and its always good to use a PSU calculator which can be easily googled.