It would be 100% bottlenecked. I had an a64 twice as fast as your p4 and even on a radeon 9800pro, my game performance shot up when I overclocked the a64. When I upgraded video cards without uprading the cpu, I saw little or no performance increase in games. I remember putting a geforce3 ti200 in my 1GHz Athlon tbird and I wasn't blown away till I got an xp2000+ OCed to 2GHz.
You can sell that video card for alot of $$$$$$$ since it's agp and buy a faster pci-e card and get a core duo and overclock the cpu to 4GHz.