Okay, I just read the score of someone's 4200 128mb
He ran it on a P4 2.53ghz, 512mb DDR 400 system.
He made 9490 3DMarks.
So maybe your 8500 is as good as it gets on an Athlon 1.6ghz?
My ti4200 64mb runs on an Athlon 1.73ghz, 512mb DDR333 system. w/o overclock, my ti4200 hits 8900-9100 3D Marks.
After overclocking from 250/500 to 290/300, my 3DMark score has hit between 9600 and 9750 marks.
But again, those scores are due to the ti4200 64mb's higher clock speeds.
My card runs very stable at 290/300. I would think you could push your card's default 240/444 to 250/500 w/o problem.
But since you said w/o overclock, Im guessing you really dont want to.
So,have you turned off AA in the 3DMark test setup? That will help you get a higher score.
~m0j0