I'm looking at a couple of different cards. Right now I'm running 2 ATI HD 4890s in crossfire. Frankly I don't think that many games are taking advantage of the crossfire setup. So I'm looking at just going with a single card this time. I've been looking at the new Nvidia GTX 660 Ti, GTX 670 and the AMD 7950. That puts me at least 4 generations past my 4890, which should be a noticable upgrade. I'm not a big believer in upgrading every generation. The gain isn't worth the cost. So I tend to spend a little more at the outset and look to upgrade in a few years.
My advice is to avoid the AMD HD 7000 series cards. I bought a 7970 about 4 months ago and it's been a headache. Shogun 2 crashes within 10 minutes of boot-up every single time I try to run it in DX11. This is a widespread issue and affects every 7000 series card that's paired to a CPU that doesn't use Socket 1155. There are reports of similar issues with Anno 2070 in DX11 mode as well. I've also had problems with random PC lockups if I have an HDMI cable plugged in and connecting my TV to the video card. There have also been problems with Adobe Flash either not displaying video properly or preventing Windows Vista and 7 from shutting down properly. I haven't experienced video corruption but I often have problems with my PC hanging on the shut down screen so I have to power down manually and then go through the BIOS screen when I boot up again. I don't know if this is related to the Flash issue or not though.
I am really happy with my GTX 560 Ti so I expect that any of the 600 series will do you just fine! 8)
The real question I have and it's hard to get informationn is whether or not a single GTX 670 or 680 performs substantially better than my XFX ATI HD 4890s in crossfire.