...Don't want to use usb as it degrades the audio and video....
No.
No it does not.
I'm not sure what shenanigans you think you saw, or maybe you actually had, but a fast USB interface will have no issue with the highest quality video you can possibly throw at it. If you were watching a MOVIE, then it is possible, however unlikely, that your PC has I/O issues and couldn't keep up with the data rates of the content on the drive. This is atypical for a highly compressed movie which is stored on any hard drive. Music will never have such a bottleneck. I have seen some video jumping when my PC has had I/O issues and when I've used underpowered PCs for video playback. I have no such issues with my more recent generation computers or laptops.
I am leaning towards a streamer or hard drive player which accepts internal 8 tb hard drive, a high-end quality model with strong processor plenty of ram and features. Any advice please.
The ONLY media players I was ever really aware of which had a integrated hard drive bay came from Dune HD. So, something like this...
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Calling it 'high end' is a bit of an overstatement. You can get much better quality these days from a micro-form-factor computer running Kodi or Plex.
I would go so far to say that Plex is one of the best possible ways to move video around your home (and the world) from a hard drive, depending on what file formats you are using and how it is stored on the hard drive.
If I really just wanted solid playback from a hard drive and wanted it internal, I would just get a home theater PC and call it done.
In reality, I would get a nVidia Shield and plug it in USB and see that the right player has no USB issues.
It's zeroes and ones. USB doesn't care. SATA doesn't care. Neither does your computer. What you said is factually impossible. Impossible. Period. Which isn't to say you don't have other PC issues which are causing some hiccups.