You're not going to gain any benefits for either one of the two, one is CPU limited, the other will be video card limited. You gotta have both to get them reach their full potential.
If you can spend $250 for CPU/mobo, I recommend the Tbird 800 with an MSI K7T Pro2, plenty fast, very overclockable.
If you can spend $200 on the video card, see if you can find a cheap GeForce2 GTS, if not then the Radeon DDR will do.