I am hunting for a laptop. That will be my first one. The Acer model below is what I am thinking from Newegg:

Acer Ferrari 4005WLMi NoteBook AMD Turion 64 2GHz 15.4" Wide SXGA+ 1GB DDR333 100GB DVD Super Multi ATI Mobility RADEON X700 - Retail

I heard laptop components usually do not perform as good as in a desktop system. My concerns go to
1. AMD Turion 64 2GHz
2. ATI Mobility RADEON X700
How these two compare to AMD XP2500+ and Nvidia 6600GT in the desktop world? Performance-wise, am I downgrading or upgrading going from the desktop to laptop?