Mark, my suggestion for you is: Forget about all the preoccupations regarding how the full-range speakers are supposed to be setup blah blah, and just do the actual experiments without ANY a priori assumptions. Try all possible configurations -- SMALL vs. LARGE, 2.0 vs. 2.1 vs. matrix-5.1, various crossover frequencies, etc. -- carefully calibrate each setting, and simply pick the setting(s) best sounding to your ears.
Just as an example, my front L/R speakers are the Hales System Two, which readily go down to 35-40Hz. However, after experimenting with various settings, I am currently using them always set as SMALL, with my Hsu VTF-3 sub crossed-over at 80Hz. This is both for the 2.1 and 5.1 listening. Although the Hales do stereo okay without a sub, adding the sub really opens up a new dimension to the music (even for small chamber ensembles). I experimented with various crossover frequencies for the 2.1 and 5.1, but in the end, 80Hz was best for my gears, room, and taste.
And the theory dictates that, even if you crossover a full-fange floorstander at a relatively high frequency such as 80Hz, you are NOT “wasting” anything. By freeing up the M60 from the power-hungry, high-excursion bass duties, you will definitely get a lower-distortion, higher-quality reproduction of the above-80Hz sound components. The speaker will also be able to play much louder with less stress/distortions -- a very important factor in faithfully rendering dynamic peak sounds. Also, there is one highly relevant difference between the M60 and M22 that is so obvious people seldom bother to mention: the M60 is a 3-way design, so both the woofers and tweeter are responsible for much narrower frequency ranges, being relieved from the added midrange duty. This alone should result in much lower intermodulation distortions and driver resonance as compared with the M22, especially at high sound levels. Comparative impressions from many people here attest to it. So, even if you end up with setting the M60 as SMALL with an 80Hz crossover, the M60 would still retain distinctive sonic advantages over the M22 (even though their basic characters are very similar). Your additional $$$ were well spent anyway, I guess.
