Go SLi bro. Go 770 times 2. Seriously. And AMD in Crossfire would suck ass. Period. Single card is debateable but in double card its nVidia all the way.
Some Benchmarks on Ultra been getting Awesome Results but a Kid on youtube was getting 92Fps n F1 2013 Ultra Settings I am not getting no way Near that,,,,
This is the Second Card I bought From Scan ,, I bought my GTX580 And when I installed my Xeon Quad Core I stripped my PC Down and rebuilt it ,,,,
But the GTX580 Was saying Correctable PCI-E Error in slot 1 ,,,,,,,,,
Thought it was my Motherboard but Installed this 780 Earlier and the error message is now gone ,,,, So there is issue with my 580 Somewhere,,,
But this GTX780 I Did a 3DMark Benchmark earlier and it was saying after I had done that I was inbetween a Gaming Laptop and a Highend PC,,,,,,,,,
But it said the Memory Clock was 500MHZ And should be 6000Mhz not sure....