If you need more power, go with the single card solution and bypass all the potential crossfire issues. I would always go with the single card solution first--if you need more, and there isn't a better card, only then look to crossfire. Also, you should catch the potential price-drop of the 79xx series, too. Assuming that AMD will try to match Nvidia pricing
But then again, you could just go with a gtx680. They're both beasts--Nvidia has the upper hand with drivers, though, in my opinion.
But I will surely tell you, if I could manage to give up eyefinity gaming, I would go back to a single 7970 in a heartbeat. The headache of crossfire isn't worth it, especially if you can avoid it. The crossfire numbers look great on paper and in benchmarks, but the quality of gaming isn't as good as with a single card. For example, in BF3 with my xfire 7970s in eyefinity, 80 - 90 fps feels almost as good as 50-60 fps did on a single gpu. I am highly sensitive to micro-stutter, and it's driving me insane.
Want to know what my first thought was when I upgraded to a second 7970 and used crossfire? WTH, this is worse than a single card. Yet I was getting 80+ fps. Not the best feeling when you just spent money on a new 7970 + Block + Backplate + I/O bracket. Save yourself the frustration, go with a single card.Edited by svthomas - 3/28/12 at 8:54am