I am currently running my main and one alt on the first core, and the other 3 on the second core. I dont have too many issues except when im in a city (terrible jumpy lag). Although i've been thinking about trying it out so that my main (which i run alot of mods on since im a mod whore) is one one core and the other 4 are on the other core.

On a side note, i have 2 hard drives as well. I've been running the instances of WoW on the HD's the same way im doing the cpu's and i've been wondering if i should switch that as well. Having my main on the first drive and the other 4 on the second drive. Anyone w/ any thoughts on whether that would make any difference?

I'm not really sure how much that would help if at all really. And i know the mods make a difference but its hard to get rid of mods that you're so used to having.