I could not find any pages comparing the 2 cards, how ever I found the same site comparing the 2 cards in different reviews.
Review of the x1600:
http://www.anandtech.com/video/showdoc.aspx?i=2632&p=2
Testing of the x1400:
http://www.anandtech.com/showdoc.aspx?i=2766&p=11
Comparing Day of defeat at 1440x900
x1400 gets 15.21 FPS
x1600 gets 42.7 FPS
Huge difference.
Bottom line is that laptops are not for gaming, you simply can't put a very fast video card in them for many reasons. If you want to be able to play the latest games for the next 5 years, it won't happen, even with a desktop, I’d recommend you keep the laptop for mobility, and then get a desktop for your gaming needs. Or get a new, low end laptop and a nice desktop.