Eddie, with the couch right up against the back wall it's unlikely that you'll be able to make effective use of a back surround speaker, since the idea is to have the sound definitely coming from behind you, not above you, and you don't have the space for that. One other idea that's been tried occasionally with modest results is to put the speaker on the floor behind the couch(despite the rear port)and pointed up at the ceiling.

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Enjoy the music, not the equipment.