I just clicked on the Guru article on the SLI 560s:
http://www.guru3d.com/article/geforce-gtx-560-ti-sli-review/5
Theres not really a lot between two 560s and two 480s, the 480s are around 5-10 fps better than stock 560s for the extra power consumption.
If you arent bothered about power consumption / performance though, go nuts and order 2-4 GTX 480s.
Man, dont do that! The GTX 570 is BETTER than a GTX 480!
You mean better cooling, I would not go from a 570 to a 480 even though 480 is technically the better card.
I just lol at Gurus charts, check the below review out, a 1000 core 560 can't match a stock 480.
Replace the 1 with an x in the link.
http://www.he1us.net/content/item.php?item=28624