You could try some wall treatments if you don't like the sound. I think centering the TV would open up the room a bit as the couch could go all the way against the interior wall (or much closer to it). Speakers regardless of free standing, in-wall or in-ceiling really vary in price so it...
Sorry for the delay in responding, but the seating location is a factor. Not knowing that I would recommend that you place the speaker closer to the TV to minimize reflections off the side wall. Depending on your seating location you may want to use in ceiling home theater speakers, the window...