Hi all, I'm in the process of purchasing a new receiver and after some advice. I currently have an Onkyo 626 with QAcoustics Q2000i. I wish to upgrade due to me having a Sony X850C 4K TV and the 626 only being 30 HZ. My basic needs / wants are the following: 4K with HDR I play PS4 and XBox One (I know neither do 4k gaming, but they only output at 30HZ on the 626) I will be getting an UHD 4k Blu-Ray Player soon. DTS-HD MA, DD True HD, Dolby Atmos and DTS X (I know the latter would be coming in firmware updates on some receivers) I have a 5.1 setup currently I presume my current speakers will still be fine and would like to stick to Onkyo's. The two I am looking at are the 555 and the 646. Would there be much difference as I can get the 646 about £100 less. I only have need of 3 HDMI ports (PS4, ONE, Blu-Ray player) but would like them to be HDCP 2.2 (so they can do UHD and 60HZ if I am correct). Also, would there be anything in more recent models that I would be missing by selecting either of these two? Thanks very much for everyones assistance.