SLI setups are very dependent on the latest beta drivers and even then there are compatibility issues with some games, which is a bit of a pain. Another thing to consider is the power consumption, running a higher single card could be better for your power-bill in the long run. One card also means less noise and heat, which is why I have stuck with a single card setup. Two 570's should be more than enough for 1080p for the foreseeable future. On a side note Farcry 3 doesn't run that great in DX11 (on my 560ti @ 1080p) so I ended up running it on DX9 on very high instead of low/med on dx11.