We are a Bluesound dealer the m66 is an incredibile unit and Iwould not worry about the idea of a dual preamp
If you max out or nearly max out the mcintosh volume pot you can then raise or lower the volume on the m66 or we can modify your mc to have a line in without volume we have had techs do this for us or you can trade in the mcintosh for a pure power amplifier
DAVE AND troy
AUDIO INTELLECT NJ
NAD DEALERS