I may be totally nuts but I think I perfer the sound when I use a usb to ethernet converter to receive music versus the built-in ethernet port. What got me thinking about trying the usb port instead was this post, though a few years old it talks about the ethernet port being quite noisy:
I had a Cable Matters usb3.0 to ethernet adapter laying around so I decided to try it. Initial impression is that music is smoother. I need to compare more.
FYI, I use my Pi3 and Rune as a renderer on my network. I also use a HifiBerry Digi+ board outputting via coaxial to my Mutec 3+ reclocker.