Hey i have been trying to make a good gaming computer on both Ibuypower.com and cyberpowerpc.com and i have made this one. Im not sure if its good or if Im missing anything. If i can get some feedback or comments on how it is or how to fix it.
For your purposes there are two things I'd change. First I'd switch the cpu to the new i5 760. It's cheaper & the i5 comes highly recommended by Tom's Hardware as a gaming cpu. It will be more than enough for what you want to do. Secondly I'd change the video card to a new GTX 460 1gb. That card should do everything you want to do & do it well. Of course you could always run two in SLI if you wanted.
There you would have an awesome cpu & gpu for just over $200 each & should easily be able to play WoW without lag.