I'd like to run 5 instances of WoW from a single PC, and I'm trying to determine what upgrades are necessary to do so comfortably.

My current rig:

ASUS P5B Deluxe
Intel Core 2 Duo E6600 2.4GHz
2x1GB G. Skill DDR2 800 (HZ)
NVIDIA GeForce 8800GTX
Windows XP
2xNEC MultiSync 90GX2 19" LCD (1280x1024).

So I'm thinking the obvious upgrades would be another 2GB of the same memory (http://www.newegg.com/Product/Produc...82E16820231065) and the Core 2 Quad Q6600 (http://www.newegg.com/Product/Produc...82E16819115017), which would only set me back $400.

But would that be enough? Would I have to run the instances at lowest settings to get a seamless frame rate? Could I at least get my main instance on full details with the alts on minimum? Would switching to Vista for the larger memory utilization be helpful or hurtful?

Is there any other hardware I'm going to need to be successful? Thank you.