For starters, use the default benchmark. That way we can compare it to what others normally use. Comparing a custom benchmark means nothing. If you force FSAA, and run it at 1600x1200x32x32, then it will be slow.
Since I have an Abit KT7, GF2 GTS, and a Duron at 935MHz, your numbers should be at least as good as mine, (and others with identical systems), as long as you do NOT use W2k. Best results seem to be with 6.47 drivers and DX7.1. Don't forget the VIA 4in1 and the VIA AGP patch 4.03 or higher.
1024x768x16x16 or default scores around 6800 to 7000 with above systems. (W2K scores less).
If using default benchmark, and your scores are below 6200, then there is some serious adjustments that you could make to improve things.
Another thing is your upgrade method. Many have gone from V3 to GF2, and the only 100% correct way to do it is to format and reinstall windows. Otherwise, the 3dfx card will leave some data in your system that will affect it's performance. You can edit the registry, and delete known 3dfx files, but somehow a little of the 3dfx stuff remains. Almost like a virus to get even with you for removing the 3dfx card.