I just bought a Toshiba P100 with 1 gig ram, Nvidia Go7600 with 256mb of ram, and a Intel Core Duo T2300 (1.66GHz).
Most of the cpu tests I have done have put it about equal with my AMD X2 3800, the graphics tests have my Go 7600 lower than my x800xl but if you get a 7800 you should be fine for gaming.
As far as noise goes, this one isnt that bad actually. The fan kicks on every once in awhile even when I am surfing the web but it doesnt bother me that much. If you buy a notebook that feeds its fresh air through the bottom you can get a "notebook cooler" that elevates the notebook and has larger, more efficient fans blowing into it. This will help keep the whiny internal fan from coming on as much.
I have found that the 7200rpm notebook drives are ALOT louder than the 5400rpm varity. My 5400 in my external drive enclosure is silent but my 7200 has alot of ticking noises.
I am happy with my notebook even if it isnt silent
Antec P180, Phantom 500, Sapphire Pure Innovation MB, 2 gig OCZ ram, 1 Hitachi T7K250, 2 Samsung P160 and 1 Samsung P120, Pioneer DVR-108, Sony CDRW, Hauppage PVR-350, ATI X800XL
Notebook: Toshiba P100, Intel Core Duo T2300, 1 gig ram, Nvidia Go7600, 17" SXGA, 100Gb 7200rpm hd