Because your room is square, standing waves will *always* be a problem as long as you place the speakers "conventionally" along either wall. If I were you, I would experiment with placing the speakers diagonally in the room, where the speakers would flank a room corner.
And you might consider toeing the speakers in the same direction so as to be firing the sound to the right as you look at the speakers. Doing so will help to eliminate early reflection points which tend to "smear" the sound and reduce the 3D effect.
Bass traps in the corners would also probably be a good idea. This will help you eliminate bass frequencies that tend to load up in the corners...
And you might consider toeing the speakers in the same direction so as to be firing the sound to the right as you look at the speakers. Doing so will help to eliminate early reflection points which tend to "smear" the sound and reduce the 3D effect.
Bass traps in the corners would also probably be a good idea. This will help you eliminate bass frequencies that tend to load up in the corners...