I think wow only covers 512mb of your video card.
Everquest and EQ2 ( old games i played on an old Athlon ) + 6200 oc'd geforce hah.
You should see the new MMO's coming out..
Check them out on Youtube : Tera or Terra - they took Lineage 3's engine, maps and some other things to do with building the game.
Lineage 3 will be out 2011
Also, it's more of a Linux and PS3 game but, Dark & Soul.
Anyways, if its going to be any upgrade. I'd look at the 4870 but, that might put you in a spot to have to upgrade the PSU aswell.