P4 vs C2D

Will a, say, 2.00gHz Core 2 Duo make a significant difference over a 2.4gHz P4 without overclocking? Relatively new to CPU upgrading, and I don't want to spend $200 for a tiny difference when that could go into my gfxcard fund.

there are no good dual core motherboards with an AGP slot, I've looked. You can't take your 6800GT with you, Dorothy. That's why I'm still using a P4.