Upgrading...Which part first?

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

Ugh! That video card is by no means a "mid end" card. The 8600's are craptastic for performance.

Get a better card and no you dont have to go ballistic with it. An 8800 series will blow that 8600 out of the water.

Then since your on vista I would upgrade the ram.

Your processor is fine and with a better vid card and a lil more ram you should be able to run all 5 wow's from one PC. Definitely the 3 you want to run at this point.

I have a very similar build to yours the only difference is I have an 8800gts card ($129iirc) and winxp with 3gigs ram. Otherwise my processor is same as yours AMD64X2 2.1ghz and I have run 3 instances with full graphics and averaged around 50fps on all three.

Actually I can honestly say I have (had) almost the EXACT same setup, and you will get WAY more bang for your buck upgrading the memory from 2GB to 3GB than youw ill upgrading the videocard. I have an 8600GT, 3GB memory, 2.2GHz dual core athlon, and I 5box just fine (1024x768 on main, 800x600 on clones). The memory is what allowed that.

Also the other thing that helps a LOT is that I have 2 hard drives, have my main and 1 clone on one and 3 clones on another, helps a TON. THEN after that I would worry about the video card, but thats also the most expensive part you can upgrade (next step up to an 8800GT is like $130 which is way more expensive than 1GB of memory and a second hard disk)

The graphics card is overkill for wow get more memory.