If you have the money to spend, why not go ahead right now and do SLi 570s?
mmm what is your monitor resolution? No game really requires more than a 6950 for 1920x1200 resolution. A 570 is stronger of course, but a 580 is an overkill for 1920x1200. Bigger or more monitors change this quickly.
Well im going to buy a 1920x1200 monitor, with my build. but thats not included in this build. so? what do i do? I might But mabye go 2 monitors at the most!
For one monitor then 570 is enough. If two monitors, well then i support 6950 crossfired. Your psu should be enough.