The KT266 isn't too bad (although the 266a is a lot better), but really I'd wait as long as possible before getting a new board. Although the real value of the new chipsets and related features (such as higher RAM frequencies and AGPx8) have yet to be established, the performance increase you'd get is unlikely to offer you real value for your dollars.
Hang on for the new AMD Hammer and related boards & chipsets. It's not easy to wait, I know. I have a 1GHz Duron and a TNT2 Ultra with 128MB PC133 SDRAM (*hangs head in shame*) and I can't wait to upgrade. But when I do spend my cash, I want the best deal possible, and there's too much around the corner to think about buying now.
Sex is great but it's no substitute for the real thing.....