It's not even close to "Best" for WOW, but should run WOW on low, maybe medium settings.
The issue with that system is that the power supply is very likely to be crappy for any type of video upgrades, and the video card that it comes with is not very good for games. You want a system with at least a 300 watt power supply if you want to play games on it or you will not be very happy with it.