Honestly, the original post's build is MORE than enough to run WOW at max settings, as WOW isn't a very demanding game. I would agree with the second poster about upgrading to i5 and perhaps a GTX 760 or better yet an r9-280(280X if you'd like, pretty much same as 7970) and you should be future-proofed for several years to come. Soon, games will start actually making better use of quad-cores...and as Battlefield 4 has come to show, that can be pretty important to have, so an i5 will be beneficial there. There-again though, you'll have to upgrade your PSU for the upgraded parts.
Regardless, if you're looking to just play wow, you've got a nice build there that should run wow at max, and most any other game at pretty close to high settings at 1080p resolutions with bearable framerates around 25-30fps.
don't be afraid to go with AMD for your videocard. With every pair of videocards between AMD and NVIDIA, AMD is wiping the map with Nvidia in terms of price/performance. I've gone AMD this time, been a long time...no regrets. for the price of a GTX 770 you can get an R9-290 which will humiliate the 770, and will also outpace the 780 by a small margin. Jussayin....and I'm usually an Nvidia guy....