heh, sorry for the confusion
that was so obvious I didn't think it required clarification

realistically, my choices with RAM are limited to DDR2-667 or 800 due to price and availability
my question on the 400's is largely a theoretical one

so does anyone know why (besides OC) should I use DDR2-800 with E4400?
(note that I'm probably going to buy the 800 anyways, but I'm curious)

edit:
found out from a friend of mine that overclocking is indeed the only reason for DDR2-800. i'm going to go with this setup for now and probably upgrade the mobo somewhere down the line.