I am looking to pick out a new GPU for my PC. I built this PC around 3 weeks ago, and my fan failed in my GTX 760, so I had to return it. I have a 550W PSU, an FX-6350 and 8GB RAM. I was looking at either the 680, the 770 or the 7970. Also a possibility to do an SLI/Crossfire, I'm just not sure how my PSU would handle it. Thanks.