7550,
It all comes down to what you are wanting to do with the notebook. (Knowing that answer really helps narrow down a good set of specs to shoot for.)
I do believe that the Centrino Chipset is the best option for a notebook. If you can go to a 15" monitor, it is well worth it too.
Take Care,
Richard
P.S. Since all notebooks come with WinXP, having 512Mb of RAM will give you the full potential performance out of the notebook.