I can't speak to the optical portion of your question here - but I do know I swapped out my normal, everyday ethernet cable with an "audiophile grade" CAT 7 cable from Pangea. And it introduced the absolute worst ground loop/ hum into my system that I have ever had. (And, I'm still confused about how that happened... I can repeat this, and tried two different cables from them with the same results if anyone is interested.) The optical connection has the potential of reducing ground loop issues, but if you can't hear a hum/ buzz now, it most likely won't make much of a difference.
