Bob, it's good that you're enjoying your M22s fully now. mine were great the first time I used them and haven't changed in nine years and well over 20,000 hours.
Sure, if you used EzSetEQ to set up(which you should)the M22s were undoubtedly set "Small", so selecting Stereo mode will automatically use the subs, the amplifier makes no difference. If you set up manually, set the M22s "SMALL" and with an 80Hz crossover.
Since you mention two subs, it's worth asking if you've placed them in positions to minimize the effect of room modes on bass smoothness, e.g., at mid-points of opposite walls or in diagonally opposite corners.
