If dell doesn't offer the card, you can't swap it in, period. Dell uses a proprietary formfactor for the vidcards (it's neither AXIOM nor MXM, but kind of a little bit of both), and they're only swappable between a few laptop models. So, if later down the line, Dell offers a 1705/9400 with an X1800 mobility, you might be able to talk a phone rep into selling you one, and swap that in (along with updating the BIOS to recognize the new card).