He likes to push a particular brand music server. IMHO, there's not much difference from a network file server if you are computer literate. I can access my entire music library on my home file servers from anywhere there's an Internet, including my phone. That said, downloading is probably best. You can stream under those conditions, but you'll lose any high-quality bit-rate because of the network response rate. At home, the file servers are available at 100% high-quality res from any digital device with a music player.
A regular file server also doubles/triples/etc. as file storage backup, and digital movie files, too. I can stream 1080 Blu-Ray from my server room upstairs to the basement big screen - all wireless. It's not magic, any file server can do this with little effort. Purchasing a specific music player file server reminds me of the old music CD recorders. They didn't last long because they offered nothing over a computer CD drive and the computer's CD drive could do so much more.
EDIT: If you are interested, look at Plex. It down-samples to a lower bit rate over the Internet, but accessing all of your music from hundreds (or thousands) of miles away is still pretty impressive.