On the left or right corner (I can't remember the default position) of LFS there is an FPS (frames per second) counter.
Select a car and check that counter while you are in the start/finish of blackwood.
Now, from within LFS change the resolution to a lower one like 800x600 or even 640x480. Then you can try to turn off AA&AF also.
Check the counter again. Have your FPS raised? Then you might benefit from a better card. If not, it means that a new graphics card won't do you any good.
My rig is a
[email protected] with 1 gig ram and 6800GT card in AGP. I have 8AA & 16AF and at 1024x768 I'm getting 100fps with the bf1 at the start/finish of blackwood.
If I change my resolution to 800x600 or 640x480 I'm getting no FPS increase, which means that LFS is CPU limited at this resolution. If I increase the resolution to 1152x864 I still don't see a frame drop. But if I set it to 1280x960 my frames drop to 85. And if iI set it to 1280x1024 it drops to 75!!
This means that I need a better graphics card if I want to run LFS at 1280x960 and above. Do this test on you own and you'll find out if you need a better graphics card.
For the record the 6600 is much better than the 6200 and it matches nicely with your P4 3.0Ghz.