Thats very expensive, You'd be better suited trying a couple of other Manufacturers. Novatech are very good, I've used them frequently in the past. Using a Laptop, even one as decent as that would be fairly dodgy for running 4 Characters. I'd recommend a Quad Core box with about 3-4 Gigs of RAM and 2 Video cards, to be safe.

Gaming on laptops (even ones designed for gaming) is never as good as a Desktop machine, so if Multiboxing is the sole purpose for getting the extra computer, then a Desktop would be far more beneficial.