I'm running 5 WoW clients on an nForce 780i, Q6600, 6GB RAM, 10K RPM Raptor HD, EVGA 8800 GTS, 2 x 22" monitors, and I run at 40 fps on my lead character and my alts are capped at 15 fps. Rarely have any problems from my setup, so you should be much better off than me with the system you're building.