New Multiboxer needing Machine Bulding Advice

Hello, I've been reading around and i Learned how to get a basic software setup going, with a mage and a pally, got them to 50, Then retired them because I wanted to jump to 5 Boxing. Currently my setup is 4Shams on my Main PC and a Pally on my laptop, using keyclone to allow them to interact. My problem is, whenever i enter (or go relatively Close too) a major city, the game becomes unplayable, and entering shat causes some clients to crash, so iv'e decided to build an entirely new machine, although im having difficulty picking the parts i would need to run 4instances of WoW (prefferably 5) without FPS/MS Issues, does anybody have any pointers/advice as to what sort of parts i should be looking to get?

Thanks in Advanced.

There's a lot on this in the hardware forum. The basic run down is a quad core processor, 4+ gigs of ram and a 8600 or better video card to run five at reasonable frame rates.