Reading over on Tom's (Shocking I know, but this actually is a semi decent article for this particular topic) it looks like the latest WoW release is actually much improved when it comes to visuals and capable of taking advantage of high end graphics and hardware
http://www.tomshardware.com/reviews/...e,2793-22.html
As it turns out, CPU is in fact the BIGGEST investment you can make to a WoW centric PC.
Part of their conclusion:
"And how about processors? After all, games are impacted most forcefully by the power of your GPU. WoW, it appears, bucks that trend to a large degree. Without question, we see the best performance on Intel CPUs with remarkable scaling from 100 FPS down to 60ish frames per second with a GeForce GTX 480 at 1680x1050 (Ultra quality) as you shed clock rate, cores, and cache. "
Looking at this chart, it's pretty clear that the biggest improvement can actually be gained by going with a high core & cache CPU. I say this because while upping the clock speed from 2.93GHz to 3.73GHz netted an average of 10-13FPS improvement, going from a Dual Core to a Quad core resulted in a 20FPS jump.
Potentially this could be a result of GPU bottlenecking as well.
From what it looks like, a GTX 560 Ti would be the most ideal pairing for 1920x1200 and under gaming, as well as "cost effective". If you go below that in terms of price/quality, start to look at competing AMD offerings like the 6850.
JJJthomps build looks to be the most ideal IMO, though from the sounds of things, I would swap out to an equivalent NVIDIA based card.