You'll have one heckuva system. Make us all jealous.
Dell does sell some hardware separately. Did you go to their website???
Probably won't be long before it is available through normal outlets.
According to ATI's customer support. They informed me that "companies such as Dell, IBM, and HP all incorporate this card in their systems. The way it's looking, the x800 SE is only available in their systems. Meh.
I'm currently in the process of contacting these three companies with hopes of relieving them of one of these cards.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic