youd be looking for something with either of these 2 graphics cards
GeForce Quadro
Ati FireGL
these as far as i know as the only CAD intensive video cards... dont try and do some 3d work on gaming cards thats just not goign to work that well eh...
i know the toshiba m5 has the FireGL, so do take a look at that because the m5 is seriosly an awesome lappie eh... but ya, look around for lappies with either of these graphics cards - that should eliminate about 90% of all laptops so you wlill know hwat youre choosing from