If my math is right it seems you have your speakers 2.5' away from the side walls and 10' apart. The first thing I'd do is try moving the speakers closer together and possibly a little further out--maybe try something like a 7' or 8' equilateral triangle setup. In any event, I'd want the speakers a little further from the side walls to let them open up a bit and decouple them more from the room. Best of luck.
Tim
Tim