this site builds comps out of parts you want.
e.g. amd/nvidia amd/ati or intel/nvidia intel/ati
but even if you go w/ a site like that you can still buy a barebones system, something that may have the mobo, hard drive, and processor, then put in a vid, card and soud card, and other things. those things are all verry easy to install, and can save u more money, not as much aas starting from scratch, but it would be better than buying a full gaming system off the shelf