Re: What video card?
I know from experience that you can't use CrossFire on more than two monitors. If you wanted to use that mode, you'd be restricted to two active monitors. SLI I'm not as familiar with, the last time I ran SLI was back in the 8800 GTS day.
I currently run my dual 5870's in CrossFire with dual monitor for gaming and most general use, and then I turn off CF when I want to activate a third monitor for a short time. It works pretty well. The 1GB cards should be fine for that resolution too, by the way.