i ran the following setup for a very long time:

amd athlon 3800+
2gb ram
8600gt 256mb vram

and i would get 20 fps in shat, and normally around 40 - 60fps everywhere else. I was running vista full aero settings and wow at full gfx as well, at 1680x1050. I could also run things like the zune software and teamspeak in the bg and not get any problems. this was with one wow. i could run two at lowest settings and get around 30fps in the starting zones.

So overall you should be getting much better performance than i used to. (ive upgraded since)