if u dont care much about oc'ing your cpu, why dont u try oc'ing your pc2100 and see if it runs 166. if it does then u can run stock speed for what u already have, if it doesnt then find some inexpensive pc2700. or if u want to overclock to get more performance, see how fast the pc2100 will go, if i i doesnt oc well then get some inexpensive pc3200 that will give u a little headroom...