Personaly I would go with the 6800 Go though I will admit to knowing nothign about the X1400. What I can say is the 6800 Go is a Desktop 6800 shrunk down to fit in a laptop conifguration. It should have 12 pixel pipes running at an insane Mhz (at least the Go ultra was
). It should handle most modern games at deceent resolutions depending on eye candy level.
The X1400 is news to me, I've never heard of a laptop or desktop variation. I've only heard X1300,X1600,X1600,X1700,X1800,X1900 with the respective derivatives of each. I'd be a bit catious about buying a card I've never heard of.
If you want benchies on a 6800 Go, search THG for the first iteration of a Dell XPS laptop. It may have more CPU horsepower than the CPU your getting but it should give you a ball park.