If you have room behind you to mount the rear surrounds say 4-6' back then direct radiators like the M3s would be best IMO and for side surrounds I would still go with the QS8's if they are mounted within 4-6' of the listening position and in my experience they usually are. Other wise the extra distance to the listener will allow a direct raditor to work nearly as well, if not better than the QS8s. The lack of height won't matter too much for the QS8s, I had mine about 2-3" below the ceiling and they worked great, as they are designed to bounce sound around the room.
Yes, I do have more than 6ft. from my seating to the back wall. As for the side surrounds, one would be within 6ft. but the other would be around 13ft. away.
