I would suggest avoiding a dual core and go for a quad core. Wow is very CPU dependent and there are various stories floating around that CPU utilization will be much higher in the expansion. If this is true then a dual core will be quite under powered imo (wow needs all the performance boosts it can get). You also have to consider that if the game is using the majority of both cores, other things like audio and just general stuff running in the back ground won't have much power left.
I guess it depends on what you want to do. From my experience when questing and in the open world, CPU and GPU wise not a huge amount of power is needed. Even running a 6970 with an overclock was more than fine for the game @ 1200p. I'm now running a 290x @ 1440p and the game runs great. When it comes to 25man raiding however, fps plummets. Sure the game is more than playable but I wish I could get more fps during raids. Generally during raids, GPU's not being used because of other bottlenecks.
Time will tell I guess.