There´s no way you can play wow smooth. Simply you wont LOL! I dont want to troll you, thats a sad true, with an i5 3570k overclocked at 4.5ghz and a HD6950 2GB overclocked also, i get in sometimes over 80pfs, but in raids my PC knees to 15pfs on a heavy fight. Why? WOW is one on the worst optimize games, something that will cut down your fps will be instances zones like pandaria, timeless isle, even the gate of ogrimmar where multiple realms share the zone, you will see your pc suffer. Playing at very low or at ultra dont fix the problem, is the game.
Everything you should look at is having better GPU (that GTX 550ti is one on the worst GPU for the money of all history) and pay a very good, low latency internet.