Couldn't help sticking one in there of my Martin Logan Monoliths I had many years ago. I've had different chairs and sofas, but the best sounding was a dining room chair, all wood with arm rests.
I had a dropped ceiling, with acoustical tiles installed, then cut out the center row and used only a frame and fabric. There's 8" of fiberglass above the ceiling, which is offset from all walls, to allow bass to be absorbed. I've tried different sub placements and since I put the dbx 360 in, I now have the subs behind my main speakers off set about 18-24." The speakers are 45" from each side wall and 42" from the rear wall and are slightly towed in.