Thanks John but I think I made a mistake here as not nearly as much volume comes out of the rear speakers as the front so if I should place them there we would hardly hear anything.
Then you have to read up on system calibration. It is explained in the primer. Basically, you must adjust the individual speaker levels so the system is outputting equal volume to all 5 speakers. Calibration is essential to getting the best sound out of your HT audio.
Mike, how far behind you will the speakers be? It seems like it could be as much as ten feet. Your room set up is not ideal, as you know, so I would accept the fact that you will have to try a couple of options to see what you like before you permanently mount your speakers.
You can try it on the rear wall, but make sure you calibrate so that you get an idea of what the system will sound like once you permanently mount and adjust. When you say that the couches are on the wall, do you mean that the couches are parallel to the side walls? In other words, no matter where you sit on the couch, your back will be to a side wall and your head will be turned to face the tv? In sucha situation, even with the speakers on the rear wall, you won't be in the sweet spot for the sound. If there was no way to turn the couches perpendicular to the side walls (or at least one of them - how many times do you have two couches' worth of viewers?), I'd be inclined to mount the speakers on the side anyway. Try and angle them down a bit so that they are not firing over your head, but it still might be better, especially if your receiver doesn't have fine tune calibration adjustments. It'll be a trial and error process til you find the best arrangement.
As an aside, are you sure that the "full" setting is for volume or gain adjustment and not a crossover (frequency adjustment)? Car audio often uses the term "full" the way we in home video use "large" and "small" settings to tell the receiver whether the system is using a subwoofer.
Yes, the couches are parallel to the side walls so we have to turn our heads to view the tv or put out feet up on the couch. I calibrated the speakers with the help of a Sony tech and what she said was that I will never get the Rear to match to the volume of the front/center becuase the rear speakers are there only to output "certain" sounds that come with surround movies and that the sound is not "equally" shared to all 6 speakers, everything depends on the source of the audio.
With that arrangement, I don't know that you need to put the speakers on the rear wall. You won't ever be in the sweet spot, so why add another deviation from a standard setup? If you can't move one of the couches, try using the side walls for the surrounds and angling them down a bit. BTW, the bigger concern here isn't the surrounds, but that you won't be in the sweetspot for the L,R,C. It sounds like you are enjoying the sound as is, but sitting directly in front of the center and in between the L and R definitely is a big part of the experience. I have one couch parallel to the screen and between the surrounds. It's where I watch tv and enjoy my theater and where the kids or my wife can sit with me. I also have two armchairs and another loveseat on the sidewalls. These don't get used unless there are 4 or more people watching and I usually opt for one of them to let my guests sit in the sweetspot. People in the armchairs and loveseat can still see the screen and enjoy the HT sound, but I know that the sweetspot couch is better. We all are limited by our space, budget, etc. We all do the best we can with those limitations. Try a couple of positions, but I think your side walls may end up being the best, even if the speakers are above the viewers' heads.