Even with an FX-8150 the i3 will probably be faster for gaming (and especially for WoW)http://www.anandtech.com/bench/Product/434?vs=289&i=126.96.36.199
Drop the 8GB of RAM down to 4GB, and even the 1TB HDD down to 750 or 500GB if you have to, sink the extra cash in to a 6770 or 7770 and you will have a much better gaming experience overall.
edit: of course, being best buy, you probably can't do that . . . so the real recommendation would be to write down the specs and buy a similar machine with a 7770 in it from a real computer store.