2xGTX260 in SLI will be similar to/a little faster than at 5870. gtx260~=4870~=5770. 4890 and 5830 are a bit better. DX11 is really all you are missing out on (well, eyefinity, but you'll be able to run triple outputs as soon as Nvidia releases the drivers to do it in SLI). If you are thinking of upgrading I would wait for Fermi to release just because it will probably cause a little bit of a shakeup pricewise (plus there are rumors that ATI will be releasing something like a 5890 around there or shortly after). You've got plenty of power for a bit, and DX11 won't really be mature and totally useful for a little bit yet. See what Fermi does to the market, and then decide.