Mostly I'm just wondering what the main difference is between these and regular Dolby 5.1 Surround. So, any help filling me in would be great. 1. Dolby Surround EX is unclear to me. 2. DTS EX is unclear to me - if that even exists - maybe I've gotten confused. 3. And, does any of this have to do with 7.1 surround or 6.1 surround? My receiver supports 6.1, so I what happens when I play a 7.1 movie? What happens when I play a 5.1 movie? Well, there's all my little questions in thread. Thanks.