Should I replace my CPU or GPU? +Rep

[Wig44.]

Hey, so I have some money from christmas and feel like upgrading something in my PC again. The problem is, I'm not sure whether to upgrade my gpu or cpu.

My CPU is: http://products.amd.com/en-gb/DesktopCPUDetail.aspx?id=400
My GPU is an overclocked XFX Geforce 9600GT, specs:
PCI-E 2.0 GPU Clock: 740 Mhz Memory Bus: 256 Memory Type: DDR3 Memory Size: 512 MB Memory Speed: 2000 Mhz

If I upgrade the GPU I'll get this (unless you have any better choices): http://www.ebuyer.com/product/238429
CPU upgrade will be: http://www.ebuyer.com/product/190673

I've got several games on the go but the game I play mostly (and one I wont shelve quickly) is WoW. Basically I'd like to know what will bring the better performance upgrade.

Thanks to anyone who replies!

[Stephen!]

WoW always benefits more from a CPU upgrade than GPU.

I would get the CPU, solely for WoW.

[LMS16]

They both look like decent upgrades.
Although I think the CPU would be the most important, but.. if u have the money, go for both of them.

Lew.