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 6" 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. when I first set up my room, I had holes for subs built, behind the main front wall.  since then, I have rolls of fiberglass in those holes and they are encased in the rear.