Nice gear!!!
I'd try switching the speakers so the woofers fire at each other instead of away. Your lack of sidewalls is probably the biggest issue, compounded by side-firing woofers.
You should be honest with your dealer and make him/her work with the system until it performs closer to what you heard in his/her showroom. That's how he sold you, so you have a right to demand comparable sound.
You might want to try turning the system 90 degrees so the speakers have sidewalls to work with (a window and a wall). It might mess with your living room arrangement, but a nice L shaped couch with the sound system on one side, and the TV on the other could work.
I'm not sure MBLs would have enough space behind them to sound right in your room. Your best option is make an agreement with your dealer to get you great sound, and if he can't, then get a dealer who can. All high end luxury items should have this type of personalized attention. If your stuck with your purchases, then tweaking speaker positions and room tuning devices are your next best bet. Look into the Lyndorf DRC if your open to digital correction. I think the 90 degree turn would be a positive change.