3500 ain't bad for a GF4 MX.
If you haven't tried raising your FSB on the motherboard, you may wish to try going down that road. I found raising the FSB by 10 MHz gave more 3DMark inprovement than overclocking the NVCLK on the video card by 10 MHz
These numbers are for example only.
10x multiplier @ 133MHz FSB = 1.3 GHz CPU
9x mult @147 FSB = 1.3 GHz CPU
The second example give a higher 3DMark than the first example with the same video card.
I used to drive a Heisenberg, but whenever I'd glance at the speedometer, I'd get lost.