Say, KenTurkey,
I'd put the LS (left surround) above and behind the couch on the side wall, near the l part of the couch and keep the RS where it is. It seems as though you might get some weird sounding action if you were anywhere but the prime listening position otherwise. I understand that you probably will only watch a movie while sitting there, but its nice to not have to always sit upright in a stationary position, and not swivel you head at all, lest you destroy the delicate sweet spot you've created.
Go with some QS8s or 4s. Place them on the half wall and on the bottom wall. Set 'em up and let em go. The angles on the speakers will probably play very nicely with your couch and will probably soudn good from more positions than the current set-up.
Good luck.
Oh, and fish don't exist. It's just your eyes getting used to watching them swim.
