If you really want deep bass you will need to add a subwoofer to the system. Your current positioning would seem to be pretty good for achieving a deep and wide soundstage. You might consider moving the speakers another foot or so apart with a bit of toe-in.
Try something like a Velodyne Optimum or DD+ subwoofer with built-in room correction in order to get the last octave of low end performance....
Try something like a Velodyne Optimum or DD+ subwoofer with built-in room correction in order to get the last octave of low end performance....