Biggest BX Bang for buck upgrade is Celery II (@ whatever)
You can get them pre-tested up to 1000mhz (Guaranteed).
I believe compuwiz1 on forsale/trade sells them here , or try fleabay.
Save yourself the time and get a pre-tested package (slotket/Gorb hs/f) and cpu. Its worth the $$
or consider the extra $100 and get a nicer P3 package. The performance of the cel 2 would be better enhanced with a geforce 2