they do come assembled. IF you are customizing one, then be sure to get a good Air cooler with it (not the stock crappy h2o cooler) and a quality branded PSU.
johnny, have you even used the site? They do not do that. upgrading from a 6870 to a 6950 just adds $55 to the price, not $200+ to the price.
(im looking right at the site now, I know what im talking about.)