My original rig was a single core CPU, 8600 graphics card, 2 gigs, and XPx32. I was able to run 5 clients using keyclone without any problems out in the world. I had to turn down/off all graphic effects to be able to run through Org though.

From everything I have read on the forums, the biggest issue with running multiple wow's is RAM. Since you will have 3 gigs now, I doubt you will have trouble running 5.