Just finished two hours of trying QS8 and M3 as surround backs (surround sides staying QS8 the whole time). It was a very, very focussed set of tests entirely devoted to DVD-Audios from Tacet who are distributing the instruments all around the listeners. Those DVD-Audios assumes you have 5 floor-towers distributed in circle, so any HT settings is bound to fail to some extent.

I finished with 15 minutes of PLx-II to finalize my "findings"

QS-8 Alone
----------
Provided they are high-enough (2 feet above hear level) and not too high (maximum 2 feet above hear level) and roughly 2-2 feet behind listener's position, they have a lot of presence and enough "direction" to identify the instruments that are supposedly behind. I really did not have time (and additional pairs or arms) to determine if my 2-2 distance is a limitation or just that I gave up too fast.

M3 Alone
-----------
More positioning, but not enough presence. Actually, the positionning might even have been annoying. But I could feel that for movies it could be good. (yes, I remembered to compensate for the difference in sensitivity!) The fact that they were carrying the two back channels with the side QS-8 might be the problem.

QSM-38
--------
Inspired by all the Frankensteins of the audio world that are positing here, I tried something new (at least for me). I extended the cables (my connectors are banana male/female so it is kid's play to connect in parallel) from the QS-8 to include the M3. Well... it works! This afternoon I will spent some time with regular music and movies, but for this very precise case (Tacet DVD-Audios), these were the best so far. Presence, direction and even a tad punchier bass.

PLIIx
--------
For PLIIx, the palm goes to QS-8 alone.

Conclusion
----------
I am seriously considering trying with M22s in the back!

See Mojo's signature