Thank you, all, for the great constructive responses. It has been quite an education, clarifying many things and raising new questions as my understanding of the topic grows.
It sounds like what I need to do to optimize my streaming system is
1. Hardwire my streamer
2. Get a linear power supply
3. Invest in an ethernet switch
4. Consider a digital to digital converter
Do I have that right, and did I prioritize/sequence them correctly?