Paul,
I think maybe your cpu or bandwidth is limiting the speed (sorry, I know
nothing about AMD). I wonder if you can try running 3DM2001 at 1600x1200 and
turn on FSAA to about 4. Then try the same thing with your 5900. It would be
interesting to see if that makes a difference.
I haven't tried the newest Cats, but so far I get a better score (2001SE)
with the 3.10s than the 4.1s.
Gary