The single 580 gets 616 total fps in Guru3D's game suite, 953 in SLI .... The 560 gets 862 fps in SLI (49 in metro 2033). This woulkd also allow you to drop down to a 750 or 850 watt PSU (ANtec CP-850 in DF, AXF Black Edition 750 in HAF).
I also think the i7-2600K is not worth it (and will loose the top performance crown to Ivy Bridge in 6-8 months anyway), for 100$ you get 100Mhz, 2MB cache and HyperThreading which might result in a big 0.25 FPS in games at most.
Moreover, unless you plan on using 3-4 video cards, I don't think you need a 1000W PSU (unless you can get it for really cheap), go for quality.