I have my 8600 working at 1920x1200 using the nv driver, however, the nvidia accelerated driver doesn't seem to support this video card yet.
I tried this but can't get it to work by editing a knoppix-generated file (which "almost" works with the vesa driver).
Could you post your XF86Config-4? Did you install the drivers from nvidia also? (I did, and perhaps this affects the nv driver?)
Me too, although I did install the nvidia driver.