I don't mean to go on a tangent but...
I have a slot 1 440 BX, (asus p3b-f) with a tualatin celeron (1.0a@1.33), and they are awesome and very inexpensive (~$40 from newegg, add $20-$30 for an adapter.) For my vid I have a GF3 ti200 (paid $63 for a new visiontek @ BB.)
Not the fastest setup in the world, but it actually games really well. The most demanding game I play is BF1942 (a notorious resource pig) and I have no probs playing it, even with vid settings pretty high and lots of people on the server. I don't feel a need to get a P4 setup since this thing runs so well.
Honestly, I would recommend something like this (since you have a good budget, go for a GF4, and you will still end up paying less to get more.) Just getting the 9700 is like putting a jet engine on a Honda, you will never, ever, ever use the full capabilities of that beast. In fact BF1942 would not even run with a P3 ~500, radeon 9700 or no.
The card will run, but is a waste of money by itself, and you will prob see no difference from what you have now. G/L
Long Live the BX!!!