Room Acoustics: Long End vs Short End placement?

I have a room that is 12X14. I currently have the speakers on the short wall about 7 ft apart. This placement produces only average performance from the Acoustic Zen Adagio. I have identifed a slight echo in the long wall corners which is creating both too much mid bass which lessens clarity. Therefore, I am going to try the long wall which is almost 12 feet of heavy glass windows, no wall at all. This will give me a bit more flexibility with placement and distance from the speakers, and can use a pair of AZ Hologram 2 speaker cables which are too short for short wall setup. In addition, I am going to try to squeeze in the left hand corner a 6ft tall bookcase stacked with books and thick textbooks. and magazines. This should at least dampen one corner---the right corner will be the site of a vertical component rack. I am concerned about a few problems in the new set-up. 1) the intereaction of the speakers with that plate glass wall of window behind them 2) Across from the speakers sits an 84 inch overstuffed couch. Behind the couch is a backwall which opens into an efficiency kitchen. The majortiy of the wall is approx 45 inches high and probalby particle board. Therefore, I am concerned about first or second wave reflections off the backwall of the kitchen.... MY Goal: to get the speakers to sound smoother and musical(as opposed to overly analytical and bright) with solid imaging. (The Adagios is a great speaker with outstanding resolution and believe it should/could sound better. I have to find some damping method for the right corner of the long wall set-up---there is no room for another bookcase. There is an overstuffed recliner which is the listener's throne in the old set-up, which always seemed to be too close to the speakers. Across, from this chair is a 43 inch panel TV which I cover with a heavy bedspread when listening and provides some damping. As you can imagine, the wife just loves the look of the bedspread over the TV.... BYW, there is an 7X7 throw-rug on the floor...... I welcome all advice and opinions. Thanks, Jim