If you buy those expensive Alienware gaming laptops, you can upgrade the graphic cards relatively easily(edit: Actually, I am not sure about this, I know you can go from 9000 to 9600 to 9700, don't know about past that). The x800 should be available in a couple of months.... or you can go with x600 which is basically a mobility 9700, but is using a PCI-express bus instead of AGP.
Here's the Mobile GPU Roadmap for 2004
ATi High End M28 Pro (PCI-E) - 16 pipes
M28 (PCI-E) - 12 pipes
M18 (AGP8X) - 8 pipes
Mainstream M24 (PCI-E) - X600 core, 4 pipes
M26 (PCI-E) - RV410 core, 8 pipes
Value M22 (PCI-E) - 4 pipes