Nathan, I'd agree with the calculations shown on the Jriver site, but not necessarily with the recommendations as to max volume. The 175 watt Axiom max spec does equate to about 110dB at the standard 1 meter measuring distance, but the Axiom power specs are typically conservative. Measuring with an SPL meter to get a max on peaks(not continuous)of 110 dB per speaker at one meter(113dB with two simultaneously, 116dB with four)shouldn't cause a problem with the M3s.
Listening out of doors with little room reinforcement(a bit from the ground), the sound level would drop off at nearly the theoretical 6dB per doubling of distance which occurs in anechoic conditions(a typical figure in home listening rooms is on the order of 3dB).
