New computer

So I'm thinking of getting a XPS 420 tower from Dell (http://www1.euro.dell.com/content/products/productdetails.aspx/xpsdt_420?c=uk&cs=ukdhs1&l=en&s=dhs&~ck=mn)
I'm just wondering how many accounts I could run on it?
Gonna hopefully try 3 boxing soon but not sure if that tower would be able to handle it properly with decent FPS

Edit: Or would http://www.pcworld.co.uk/martprd/sto...ory_oid=-35614
from PC World be any better? Just thought to go look there :)

I ran a xps 410 wit a e6600 2.4ghz and 2gb ddr2 667 and the ati x1300 pro and could run 2 wows okish and 3 was killing me. Bumped the ram to 4 gigs of 800 and then a ati hd3450 sb edition and could run 3 with out a problem. Only time that it sucks is in heavy aoes and in major cities. But did do the job for 3 after the up grades. Hope this helps