One pcie slot is good enough for me as i dislike SLI and Crossfire both, configuring SLI is too much of a headache from my past experiences so i prefer a single card solution.. If you want 2 cards in 1 get a 4870 X2, if your using a 24 inch lcd or less crossfire or SLI is pretty much money down the tubes if you ask me.. That's just my opinion on the matter, you will love that board.. It's one of the best motherboards out right now and it overclocks like mad!! Good Luck
Crossfire is not necessary though. A single HD 4870 1GB will be enough for basically every game at 1900x1200 at High/Very High settings. If you want higher resolution, an HD 4850x2 or HD 4870x2 would do that and perform better than the Crossfire Equivalents.
