you mean you want to have a "gaming" laptop?
i ever heard about alienware laptops and i've seen their specs.
They are a gaming laptops.
Here is the link for ATI gpu's specs (below the page):
http://en.wikipedia.org/wiki/Radeon_R300
http://en.wikipedia.org/wiki/Radeon_R420
http://en.wikipedia.org/wiki/Radeon_R520
For me, the best is Mobility Radeon X1800, X800, or 9800.
But i find that it's not easy to get notebook with em.
If you want x1800 simple, just buy a 20" heavy-duty dell notebooks and it's there. but, 20 inchs??
I think i'm in the same direction with you as i'm going to replace my notebook in the middle of this year.
Mine is using mobility radeon 9700 and i could play bf2, aoe3, wow and of course use the "aero 3d" from windows vista. It's 2 years old.
Acer's notebook nowadays using ati MR x1600 512mb hm , but i do not think that's a hi-end gpu for notebook as there is x1800. Especially the performance given by x1600 was not a hi jump from my 9700 which was made in 2003.
in other words, im also lookin for a 256-bit mobile gpu.
But the choices is all yours, i hope you could see the specs clearly and find an appropriate lappy for yourself. Im sorry that i could not give nVidia geforce specs as i didn't found it in the wikipedia.