You'll be able to run a single ATI card on that mobo just fine, but for dual vid cards you either need a crossfire capable mobo for 2 ATI cards, or 2 nvidia cards for SLI.
As for the cpu, right now I think the good price/performance spot is the A64 3700 "San Diego" cpu. It runs about $230-$240. There is an equivalent socket 939 opteron that is essentially the same cpu at the same price but has gone through server-grade quality control, but those are selling out fast and AMD has discontinued them because they're a better deal than the other A64s right now.
Also, consider 2x1gig memory instead of 2x512meg, especially if you can find quality stuff on sale. Not many games need 2 meg yet, but it's commonly reported on gaming review sites that BF2 will stutter on any rig with less than 2 gig memory.
I'd probably go with the x-fi soundcard as well.
As for mobo, I'd personally get an asus A8N SLI deluxe based on various reviews, plus a few overclocker websites use ASUS A8N mobos as their test bench boards which tells me that they're reliable and consistent. But YMMV.