This is nothing new. There was Quad(4 channel) in the 1970's. There was rear speaker setups like the Hafler circuit for rear ambience sound. There were rear digital and analog delay units. It was all crap.
WHat about four speakers.......
When you are in a concert hall, sound hits you from all sides. Why arent there high end systems with four speakers; the listener would pretty much sit in the center, you get a box to delay the rear speakers ever so slightly to imitate those sound waves taking longer to reach your ears. What are the ups and downs of a second set of speakers behind you, even without any sort of delay? A few of you guys must have tried this, thanks......