For World of Warcraft, I would suggest going for an i3 2100. It has
superior performance in WoW.
---------- Post added 2011-09-01 at 09:12 PM ----------
If you cut down on what Tetris suggested, i.e. the RAM, ODD and the PSU (the Corsair 430W should suffice) you can use the extra cash for a better GPU, like the ones listed. For WoW, I believe the 460 performs better, but the 5770 should be cheaper afaik. Check here for more info:
http://www.anandtech.com/bench/Product/172?vs=156.
Anyway, where are you from/what site do you plan to buy from?