THX's recommendation of 36 degrees (
and that's at 16:9 viewing, let alone smaller ARs), at 6.7 ft viewing distance, would mean a 60" display. FWIW. I prefer an even more immersive angle, however I am not watching TV on it, and most watching is with smaller AR's. If your room was mine, I would be aiming for a 60". Perhaps a 58" Pana. I know it sounds crazy to a lot of folks, but it is what it is. A couple of the more involved BD PQ reviewers at AVS do exactly that: 60" Kuro from 6 ft.
Then why blow your hard earned dough on a new sub, when much more impactful improvements could be found elsewhere?
While you will get more rumble 'n shake with a bigger and stronger sub, I'd DEFINITELY vote to spend on treatments first. Broadband bass traps everywhere would be my instinct. It'll also help out your midbass, and things should be clearer, smoother, more natural. I personally find that higher volumes can be reached because that threshold of bad SQ due to room's influence is not reached 'til much later (well, treatments do also just deaden a room some as well). Think boundaries, corners, but in a room that small (guessing, I don't know the dimensions) it could really use a bunch.
The smaller the room, the greater the need for bass traps. I would contact Mr. Pape of GIK and Mr. Winer of Real Traps to get started perhaps. Post in the Room Acoustics subforum, and eventually some experts should hopefully chime in. Oh yeah, seeing how close your mains are to the sidewalls, I know that I would put at least one beefy panel at their first sidewall reflection.
Try a 42 deg viewing angle, and you won't be liking DVD too much either, at least if you have BD on hand. Or, bring a DVD and DVD player to your local theater, and see if they will put it on for you.
Interesting. Hm. Anyhoo, the recommended angle to listener for 5.1 side surrounds is 110-150 degrees. The photo looks pretty good to me. Just don't run em too hot Phil. What did Audyssey get you for the levels there?