I notice you have your subs angled in to your mains. In my experience when the subs are angled in to the mains the sound staging MAY be effected by the angle of the subs ( and yes, I am aware that below 100hz, bass is considered omni-directional.) I suggest you try aligning the subs in parallel with the mains (even if they are still set back from the mains) and listen while paying close attention for imaging shifts, you may wind up with a wider and fuller sound stage.
