Squeezebox (Logitech)
https://en.wikipedia.org/wiki/Squeezebox_(network_music_player)
I have yet to find a music library program that has grown with me and my needs like the Squeezebox. I've been able to have my entire music library with me at home, work, and in the coffee shop without much difficulty. Getting things set up is a bit fiddly but once it's working it's a thing of beauty.