I think if you are okay getting SLI 560s right out of the gate then I think the 2GB palits would handle your surround pretty well in all but the most demanding titles, dual 560s are no slouch in processing power. In my mind the only alternative that would offer the performance you are looking for would be the 2GB 6950/70 because I don't believe there is a 2.6GB 570 available and I don't think SLI 570 with only 1.28GB would be what you are looking for.
The only other 2GB 560 I have heard rumor of is the Gainward 560 Phantom 2GB
but I have no idea if it will be available in the states or any time soon. I don't think you would be unhappy with the performance you would get out of SLI Palit 560 2GBs as long as you know that if you want to do any serious overclocking, which the 560s like and scale well with, then you would need some form of VRM heatsink for them.