Get a better graphics card. If you can, I would recommend getting a better power supply (500w would be good), and then buying your own graphics card to put in it later. Make sure that the computer is not a slimline case, as that will limit your choices.
The 315 is decent compared to most computers, and it will definitely run wow, but for around $170 you can get something more than five times as powerful.
You know, you could just build your own. I doubt it would cost much more and then you could get exactly what you wanted. It's really not hard either.