-50 db tells us it was playing at 50 decibles lower than reference. So I would not think this was too loud no matter how the volume control is calibrated. On my AVR, Pioneer SC-25, you would hardly hear it. I usually watch television at -22 db; movies -18 db. I don't think it was the volume - some other problem.
Also, count me in as one who thinks the Denon 2312 you have is not adequate for ML 4ohm speakers. I would be looking for something rated into 4 ohms if you really like the ML's. Or stick with Denon and look at a 8 ohm set. Good luck and hope it all works out.
Marantz PM15S2 LE, Oppo BDP-103, Simaudio Moon 100D DAC
VPI Traveler V2 with an Ortofon Rondo Blue and Simaudio Moon 110LP, Technics SL-1400 with an Audio Technica AT-14sa and Pro-ject Phono Box S
Dynaudio Focus 260's, Rel T-1 and a Panasonic TC-P54S1.