Audiomaze- start with the basics. FIRST thing you need to do ( once the speakers are in place and with Maggies, that will take a LOT of experimentation) is to get a decent microphone and do some rudimentary analysis of the room with a test disc/cd. Once you know what you have, then you can begin to level out the peaks with treatments/furnishings, etc. As a basic, with Maggies, you want some diffusion on the wall behind the speakers and in your case, get a 4" foam cushion to sit on which (hopefully) will raise your ear height and eliminate the back of the couch reflections. I would not try to "fix" problems that you can't identify from the tests- it is a waste of time and money. Good Luck!
