I built a machine for a coworker using this setup 2 months ago:
Intel Core 2 Quad Q6600 cpu
Gigabyte GA-P35-DS4 mobo
4GB Corsair DDR2-800 memory
2x 8800GTS 320MB videocards *not in SLI mode*
3x 22" Dell LCDs @ 1680x1050 each.

One videocard powers his main display - for his 3D work, and the 2nd connects to the two secondary monitors.

He's not into gaming much - but heavily uses 3D Studio Max, Lightwave, Premiere, and Photoshop. I'm sure it would 3-box WoW just fine though.