Peter, welcome. If you have a significant amount of room behind your listening position to form a rear soundfield(say at least 4')then yes, using a 7.1 speaker setup with your Yamaha or Denon would be of benefit.

The side surrounds being at different distances wouldn't be a serious problem since their sound levels can be calibrated so as to be equal at the listening position.

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Enjoy the music, not the equipment.