So, I have recently upgraded my CPU and my motherboard (my old one would not support a crossfire set up) and I have been debating for a few weeks now on what to do with my GPU. I am currently sitting on a single XFX 6870 graphics card ( http://www.newegg.com/Product/Product.aspx?Item=N82E168... ) and I have been running Eyefinity on that for a bit. It does tend to struggle some on a good chunk of the newer games and that forces me to bring it down from 5760x1080 to 1920x1080 or to kill the graphics down from High. I can still use it fine for games like Eve Online and such, but I have been itching to upgrade. On one hand I have the juice to run a 6870 X-Fire set up and that would only run me $140-ish to achieve, but on the other I can get a single 7970. Will I be able to get the same frame rates off of a single 7970 in Eyefinity as I could force out of a X-Fire 6870 set up? I would eventually upgrade to X-Fire 7970's, but I don't currently have the money to dump on two new cards at the same time.
sell off your 6870 and get the 7970...you will get almost similar performance as 2 6870 in crossfire x...later you can get another 7970 with the money.
also remember crossfire x does not perform equally well on all games.