I'm replacing a pair of MMGW's with QS8s. I purchased the wall brackets to go with them. The couch is placed along the rear wall, and my wife doesn't want it brought further into the room. The shape of the room eliminates sidewall placement. The only place to put them would be on the rear wall. I'm thinking that they may sound better spaced a little wider than the MMGW's. Does anyone have experience with a room layout like this?

Room Rear
Room Side

Room Front

I would forgo the seperate wall bracket and just use the 'T' bracket the QS's come with and mount them in the same place as your current surrounds. You will get much better surround feel from the QS's mounted in those positions.

BR, welcome. Yes, mount the QS8s on the back wall, but separate them more widely than the MMGWs, almost to the side walls. Keep in mind that even when mounted on the back wall they're still playing side surround material, so you want more of a side rather than back effect.

Thanks for the advice. Would a good height be slightly above ear level when seated?

2-3' above ear level is generally suggested.