There are suspected *heavy* price cuts on Intel processors in the near future.. I'd look and see if PIII gets cheaper.
Even as I myself have a celeron667@901 and am quite happy playing with it, I still know that it matches about the performance of a PIII600 even when overclocked. OTOH if youre planning to buy an AMD system in the near future, get a Celeron667 like mine.. They come cheap and overclock to 950Mhz or even 1Ghz with a proper cooler. I use Golden Orb and it posts at 1Ghz but won't load OS.