Cork, in the past Alan has discussed the difference the new tweeter makes on M22s. If he sees this he may comment, but he especially noted a wider soundstage.
"Crisper" is open to various interpretations, but may have nothing to do with the construction of the tweeter itself, but rather that the crossover raises the tweeter level to give a sense(unrealistic?)of greater treble detail.
As to the surrounds, of course the present QS4 and QS8 are non-ported for mounting on or very near the wall. These would appear to be a logical choice for your use.
I also listen to 2-channel music sources with the surrounds in use, but I'd strongly suggest using a mode such as DPLII(my preference)or Neo:6, which are designed for that purpose, rather than using an all channel stereo mode. All channel stereo simply duplicates the main channels in the surrounds, while DPLII extracts only the surround ambience imprisoned in the main channels and sends it to the surrounds where it belongs. The effect is more realistic compared to simply having all the speakers play the same material(which is okay for a party, etc., to give a more uniform sound throughout the room).
