I think he meant PCI for graphics cards. By the way, not many people's pockets are deep enough, or brains light enough, to buy an Alienware. They're extremely overpriced. PCI is much alive for things like sound cards, modems, etc, but not for graphics cards.
in short, the answer i am guessing is no, manufacturers usually dont even like you going inside your own case and they stick warrenty-voiding stickers on the back of the case
If you want to sell your PC, if possible, do it after you get a new one. Because if you sell it before, you obviously have no PC. And unless you save a HD, you lose data you could've transferred over.
http://www.monarchcomputer.com/Merchant2/merchant.mv
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