a branded machine always costs more than anassembled counterpart because the company offers support, warranty, et al. heck, u cld get a p4 spending the same dough, or an amd+gfx card.
bottom line:if u want exact price to performance ratio, go for an assembled machine. if u like peace of mind more than the machine u r buying, go for a branded machine as the dealer takes care of all your headaches
hope this helps, bye..