Since you're wanting to play WoW, you will want to get an EVGA GTX 760 w/ ACX http://www.amazon.com/gp/product/B00DHW4HS4
. It's just within your budget and will last you a few years.
I used to have a GTX 760 and was extremely pleased with the performance at 1080p. You will be able to run WoW with all the settings maxed as long as your CPU is able to keep up.