Hello, I'm looking to be running 3 instances of WoW on this comp and 2 on another pc. However the pc who should be running the 3 is getting kinda old and I was looking to upgrade it slowly before WoTLK.

This is the current specs:
CPU: AMD 2350 BE 2.1 Ghz. (This is a dual-core, which I've overclocked to 2.4 Ghz.)
GPU: GeForce 8600 GTS. (A mid end card.)
RAM: 2GB Corsair.
OS: Vista Ultimate 64 bit.

Was wondering what would give me the best performance to upgrade first. Get an AMD quad-core, or get a higher end graficscard like the 9600GT? Or perhaps 2GB more ram? Dunno if WoW likes quad-cores or not but getting one would allow me to put the affinity on each WoW so they would have 1 core each and share the last one or something. Need some advices! Thank you in advance. =D