You need to work within the limitations of the room. The rear couch is too close to the rear wall, there is nothing you can do about that due to the depth of the room. So those rear surrounds, even downward firing ones, don't make a lot of sense. The sound that should be coming from behind you will be coming from directly on top of you. What I'd suggest is forget about 5.1/7.1 for now. Direct your efforts to getting stereo sound from your 2 front speakers as good as you can. The sound from movies in PCM stereo is far better when running on some higher quality gear than multi-surround in lesser gear that are limited by the constraints of the room. And finally, many of the questions you're asking are addressed in the owners manual. Suggest you download it, read it, and anything you don't understand refer back to the forum. You need to devote some effort in helping yourself first (by reading the manual) before asking others to devote their effort in answering questions that are covered in the manual.