Some thoughts to keep in mind....
I have both an older Sony BDP-S590 bluray and also an Amazon FireTV. I don’t know the current Sony app offering, but the YouTube app on my particular Sony is not that good. It really only give you standard definition video and the audio side is not really high-def. Also, the Sony bluray players are somewhat soft sounding as a transport. Sony will stop doing firmware updates for a product within a year after it has been discontinued. I have not had a firmware update for my BDP-S390 in a very long time.
The Amazon Fire TV is an open platform (based on Linux I think) just like their Fire and Kindle tablets. It has constant app updates with a huge collection of online apps to choose from. My FireTV is one generation old, but still is able to get both YouTube and core FireTV O/S updates. The YouTube app is superior over the Sony both in usability and capability to do hi-definition and hi-resolution audio. It will provide this over HDMI to your processor. You can also stream Amazon video content.
I have tested both of these devices directly connected to my Krell S-1200 processor through HDMI.