My HDMI extends from my Apple TV 4K to a Nad m17 processor, and then I have RCA interconnects from the processor to a Conrad Johnson gat2 preamplifier which is connected to amplifiers.
Of course everything flowing through Xfinity is subpar. But all the streaming stuff going through Apple TV for nonstereo listening is hard to improve on given inherent streaming Quality deficiency.
the power cords, HDMI cables, Ethernet cords and network switch are all upgraded.
What more can be done here? Sound is quite good on my system but unfortunately it's entirely dependent on the quality of the source. And streaming Quality is inconsistent and always compressed.