I'm also somewhat uncertain about what your question is. I'm not trying to argue you out of getting the M&K speakers at the front. I was just telling you that the THX endorsement is no assurance of getting smooth, linear and transparent sound quality. I have no argument with the THX requirement of three identical speakers across the front; it's just that it's impractical in many homes and installations. It's also why Axiom developed the no-compromise VP180 center for those who can accomodate its size.
To reiterate, yes, the Axiom QS8 surrounds at the sides or rear will blend beautifully with the M&K speakers at the front.
In passing, the M80 floorstanders have useful output in a room to about 25 Hz. For the record, the only instruments with significant content below 30 Hz are the concert grand piano (28 Hz for all but one Austrian model with extra keys at 16 Hz); large pipe organ, 16 Hz, but the latter is very low level and the 2nd harmonic at 32 Hz is much stronger; and orchestral bass drum, depending on the diameter of the drum.
