First, if you haven't already, get hold of a bunch of benchmarks and verify that your OC works as you intended. Otherwise, you should maybe check up on your BIOS and cooling.
Secondly, get a better videocard. This is a fairly safe investment, as long as the next MB you buy also has AGP.
Thirdly, what RAM are you using, and what does your MB support in this field and in way of CPU? Dual channel? FSB?
Edit: - Right, I'm really getting old. Now I can't read. "PC2700", right! Got it now. Well, that falls between being sure. I wouldn't do anything about the memory then. Hardly worth it.