What part should I upgrade next?

[Dhomeli]

Hello all, I'd like to invest in upgrading parts of my computer and am curious which upgrade would have the greatest benefit.

I mainly play WoW, but also play D3, SC2, Skyrim, LoL, and Civ5. I would like to either upgrade processor/ram/cpu or graphics card, but probably can't do both at the present time.

Budget - $200-$300
Resolution - 1920x1080 (main monitor) / 1600x900 (secondary monitor, if this matters, I run games in Windowed/Borderless generally)
Games / Settings Desired - WoW primarily, I can currently run it at High but start to see fps drops in 25mans and would like to see better fps and run on Ultra if possible.
Any other intensive software or special things you do (Frequent video encoding, 3D modeling, etc) - No.
Country - USA
Parts that can be reused - I'm seeking to either continue using current motherboard/ram/cpu and upgrade graphics card, or upgrade motherboard/ram/cpu and continue using the current graphics card, but not both upgrades together this time.
Do you need an OS? - No.
Do you need peripherals (e.g. monitor, mouse, keyboard, speakers, etc)? - No.

Current Build-

Motherboard: ASUS M4A77D
http://www.newegg.com/Product/Produc...82E16813131618

Processor: AMD Phenom II X4 960T Zosma (Set to 3.5GHz)
http://www.newegg.com/Product/Produc...82E16819103995

RAM: [4x] G.SKILL 1GB 240-Pin DDR2 1066 (PC2 8500)
http://www.newegg.com/Product/Produc...82E16820231143

GPU: EVGA GeForce GTX 550 Ti SC+
http://www.newegg.com/Product/Produc...82E16814130744

SSD: OCZ Agility 3 AGT3-25SAT3-120G
http://www.newegg.com/Product/Produc...82E16820227726

[Deleted]

Do you have access to a Microcenter? (in store)

[Dhomeli]

Looks like there's one in a city about an hour away.