Hi Alan,

The PM16 is a stereo amp, this one:

http://www.thevintageknob.org/marantz-PM-16.html

Perhaps it's not surprising, then, that we had to turn the volume way up? We were comparing the level of the front speakers, fed through the pre outs and powered by the PM16, to the level of the center speaker, powered directly by the SR6004, and noticed a huge difference. (That is, until we turned the volume of the PM16 up.)