Most of the time I mine unamped. If I am it is not anything stronger than OA103, usually I stick to OA101-102. I think my skills would allow me to use stronger amps but
CND is like amped already so adding another amp increases the basic amp
CND gives. I think that the reason you don't find sizes smaller than V (or faxed V which comes as IV) is the evidence for
CND being amped.