How much for a geforce4?

How much RAM was missing from that 9800? O_o
My cost from my supplier for a 9800 Pro 128mb is something around $527, and about $15 more for the AIW version.

As for laptops with swappable video cards, there are quite a few more on the market now. In fact I think most of the big names have at least one or two high end laptops with removable video cards.

As for your Dell Sovereign, I think you may be out of luck, but check out Dell's website and see what they list as upgrade options for the model you have.