My home theater is in a family room that is 12' wide by 19' long. The couch is at 8' from the TV.

My LCR speakers are Paradigm monitor 7 v3 speakers and CC-390 v3 center. Subwoofer is a PS-1000 v3

I currently have Paradigm titans v3 hanging from the ceiling as surround (5.1 configuration) but I want to replace them with dedicated side surround speakers that will be positionned on the wall at 3' from each side of the couch.

The receiver is a Yamaha RX-V667 and I do not want to change it.

I would like to know with the size of the room which surround (QS4 or QS8) will be sufficient for the room size. On the Yamaha, I usually go from -40 to -30 sound level when watching a movie.

Could I use on wall speakers (like the M3) instead of dedicated surround speakers for the home theater?

Thank you for your help,