If your Ethernet is somehow passing noise into your streaming device effecting the sound, you have a crappy streaming device with a bad network port that was not correctly designed to work in the environment as advertised ( Ethernet) Don't blame the network. The reasonable band-aid would be an optical isolator. The only reason to go to shielded CAT-5 would be if testing shows a lot or packet resends due to data integrity. 1000' runs in industrial environments for example. Or where electronic espionage needs to be protected. Sometimes required in medical installations. Both ends of the equipment then need to be compatible for the shielding and be prepared for sneaky ground loops. Good luck self terminating shielded yourself.
Audio bandwidth is trivial compared to Ethernet. Hubs work fine. OK, if someone was a high end multi-player gamer while someone else was downloading large data files between ports on the hub then it could get congested, Isolating ports in a switch vs a hub won't really help otherwise.
As far as sound, well remember there are two definitions of sound. Those that are variations in air pressures you ears sense. Real physical things in the world. Then there is what your BRAIN believes. Imagined sound. It may be real in the physical world, it may not. To you, it is real if you brain says so it even if it is not based on actual vibrations in the air. Drink whatever Kool-Aid you wish.
A 50-cent ferrite does wonders for those "horrible" switching wall warts. If you need more than that, again, your equipment is to blame.
