You can stream your files from a NAS to any streamer (in the local network) just fine when your ISP is completely dead and gone with the wind!
On the same note dude, if you like an album, buy the artist's hires digital album (put it on your nas) and pay the artist. These streaming services pay them peanuts. On a positive note, you will have permanent ownership of that album and will no longer be "renting" it from the streaming service.