Glenn, some comments on your reply: yes, stronger and smoother bass output on music is a frequent goal, and if you're limited as to sub size I'd suggest adding a second small but powerful sub which wouldn't have to be identical to the EP175. If you could then place the two in accordance with the findings of Dr. Toole's colleagues at Harman in their paper you should notice a significant improvement even staying with the M22s. Basically this would be opposite each other at the midpoints of the sidewalls or front and back walls or in diagonally opposite corners.
As to listening to 2-channel material, I never listen to the music only in stereo, but apply processing such as DPLII to extract the natural surround ambience found in the front channels(there was no place else to put it)and send it to the surrounds where it belongs, making the home listening experience a bit more realistic.
You're correct, of course, that the "+" subwoofer setting has to be used for sub output with 2-channel material if a "direct" type mode has been set. However, I've found that the slightly lower noise level present in a direct mode as compared to one of the modes involving some processing is of no audible significance at the listening position(a slight difference in levels between the modes may lead to the incorrect conclusion that one is inherently superior)and never use direct or the "+" type sub setting.
