J. Mike, that room does really limit what you can achieve. You didn't answer what kind of speakers those are so I'll just assume they are capable of playing full range at least down to 25hz their corner placement will emphasize the bass. Here's what I'd try if I were you this will be worth the effort;
-Move your equipment rack to the front under the screen either side of the center if need be.
-Move your main speakers out from the wall, a couple of feet at least, and get your right and left as far away from the side wall as far you can without impeding your vision.
-Pull your couch out two or three ft from the back wall and place your sub behind it center of the wall (to start anyways, you might want to corner load it depending if that's an opening I see on the right.)
Then do some temporary acoustic treatments to give you an idea of what can be accomplished, once you see what you can accomplish you can use proper stuff to match your decor;
-Sit in the middle of you couch and have someone slide a mirror along the side wall starting near your front speakers and moving towards you and as soon as you can see the tweeter in the mirror mark that spot on the wall and place something there on both sides, a pillow or a small rug - these are the first reflection points.
-Temporarily place pillows in the four upper corners of your room so there's air space behind them and in the back wall corners if you have enough. These will be mock bass traps to give you an idea of what they can do.
- Cover the glass table with anything like a thick table cloth but leave the table there - you normally would, and if you take it away when measuring what the Audyssey does will be wasted because there's going to be a bunch of stuff bouncing off that glass surface. (That's likely why your center channel doesn't sound right.)
- Lean or put something between your back two speakers at ear height that has a completely irregular surface, a loaded bookcase or something - this will act as diffusion.
- Set your mains to Front+LFE - do cross over your center to at least 80hz, set your subs' level to where it sounds properly integrated with the rest of your system.
- Now run the Audyssey - and make sure you do it with the projector off.
This is a starting point as far as the Sub and center channel/ mains crossover are concerned. Try it with your mains just set to large w/no LFE, you can also move your sub around, the goal is to get a smooth bass response without being able to localize the sub.
I'm guessing a center back position for the sub because of the size of your fronts and their corner placement reinforcing the bass coming from the front.