Welcome to the forum.
If all of your music is MP3, and you don't want to pay much, you may want to try an Audiotron
. It connects to your Ethernet, and also connects to your stereo with either two standard RCA audio cables or an optical TosLink cable. You need to add nothing to your NAS, as the Audiotron, on power-up, will search your network for MP3s and catalog them. You then access them with the Audiotron's remote-control or front panel.
I have four of these, pulling music from a Synology NAS. It also has a web interface, so I control them from my laptop. I bought them for around $30 each from eBay so it's perfect if you don't want to pay much.
It will not play music from iTunes. It was designed before iTunes existed. It does not play FLAC either. Only MP3 files and WAV files.
It works well only if the metadata is correct for the audio files. If there is no metadata, it will only show filenames. You can not browse your collection by artist, album, genre etc without metadata. I use a free program called MP3tag
to maintain my metadata.
The Internet-radio is limited to stations using older codecs.