Bart, I'm also surprised that the Bryston would clip even in your setup, but apparently the combination of room size, listening level, and feeding M60s both full range plus LFE is a bit much. If the sub is as bad as your "P.O.S." indicates, get a new powered one and run all your speakers, including the M60s, "small"(which will also remove the LFE from the M60s), using the 100Hz crossover if you don't get another receiver or separate crossover to allow for more options as to crossover frequencies. Since the crossover isn't a brick-wall cutoff, but instead rolls off the sub above the selected frequency, often at 24dB/octave, the sub will continue to have some output above the crossover area.
Don't be concerned about losing any "sweet-sound" from the M60s if they're rolled off below 80Hz or even 100Hz. Those frequencies alone are in no way "sweet" or "tight", they're dull and plodding. Any such qualities in bass instruments are a result of the harmonic overtones which the sub doesn't reproduce and which the mid-range drivers handle. To illustrate this, disconnect all the speakers but the sub, leaving everything else the same, especially the crossover to the sub. Then you'll hear what the stuff below 100Hz sounds like alone.
