Hello ethanw,
Although the dB (decibel) calibration of various AV receivers will vary somewhat from brand to brand, the -24 dB level you are using on your Marantz to drive the M22s is quite normal and within the range to be expected of various Axiom speakers.
In fact, the levels you are using are almost exactly what I see on my H/K AV receiver read-out when I drive the M22s with an EP500 subwoofer, two QS8 surrounds, and a VP150 center channel, listening from a distance of about 9 to 12 feet back. Those levels typically produce a sound pressure level (SPL) averaging about 80 dB (C-weighting), measured on a Radio Shack SPL meter. Peaks of 85 dB SPL at your listening chair are subjectively described as "quite loud."
These settings may vary depending on personal taste in playback volume, how far away you sit from the speakers, the overall size and furnishings of the room, as well as the recording level on the original source (the latter may vary as much as 10 dB).
Regards,
