know ahead of time that i have much respect for both the M9 and WAMM, but that nothing is perfect. design compromises are part of any speaker.
Henry, are you claiming that integration of (X) amount of subs to an M9 or WAMM will be 'as integrated' as my MM7's are integrated? and you would know that how?
i don't personally know the process for adding OEM subwoofers to the M9 or WAMM; so the following is a guess as to how this might look. if i've missed it here then please set me right.
one advantage my MM7's have over either the M9 or WAMM is lot's more driver surface in the mid-bass, and more efficient to boot than either of those so an easier load for an amp. my MM7's have '4' 11" woofers per side covering from 40hz to 250hz. that can be done since the bottom octave is covered by the active subwoofer tower. and i have zero crossover in the mid-bass which is the power range of lots of music. my passive tower cannot be used as a stand alone speaker, as it's rolled off to perfectly integrate with the sub tower. OTOH with the M9 or WAMM you are having to somehow throttle the main speaker back to avoid doubling frequencies in the bottom octave. not exactly a fully integrated ground up approach. then there is the coherent wave launch issue. the MM7's use a first order crossover and are phase and time aligned. i have my towers equa-distant from my ears.
then there is the amplifier coherence issue. the MM7 sub towers take their signal from the speaker cable input to the passive towers, so they get the signature of the main amps into the sub input, keeping things 'of a piece'. the M9 or WAMM will typically use a different amp with the M9 or WAMM than the sub's. and the subs will not get their signal from the speaker cable terminal; it will come from an outboard crossover.
all the added subs in the world won't solve the integration issue. would anyone notice the integration limitations of adding subs to a full range M9 or WAMM; maybe not unless they directly compared it to my MM7's.
at the end of the day likely the integration of the M9 and WAMM and the full blown OEM sub approach is probably 'good enough' to pass muster. but.......if they started out as a twin tower speaker from the ground up no holds bared, no doubt they would be better even. and that is the point i am making. "integrated" comes by degrees. and fully means fully.