Hi, I am curious about the sound , between the two format of ,4k disc and blu ray ,of course 4k disc has more to offer , it's much expensive too, I am trying to buy mostly in 4k disc ,now in My collection,but some very old movies just not worth $30 to $45 ,if the blu ray version cost $15 or less at times , because I recently got the Yamaha RX A8A Receiver, so sound for me is the main point , if an blu ray disc support Dolby atmos , my question is ,that if the blu ray version support Dolby atoms ,these the 4k version still sound much better , thanks