I am looking for a NAS as a small music server. I am using a Buffalo Link station at present. My library is small compared with others. It currently is 250gb of Flac I do not see this going beyond 500 gb I have seen a set up where someone had set up a music server using the DS218j. Whilst I am sure this does the job well, I prefer the appearance of the Play version. The set up I saw was using Plex to sort his libraries which I liked and would want to include this feature. Most of the time I will play back through a Sonos system. I do not visulalise wanting to connect to the NAS externally (outside my home) so all my equipment will play the Flac media. So will the DS218 play suit my purpose, and if I set it up on 1 disc can I add a second later and arrange it in a raid situation so that I have a back-up if one disk fails.
Yes, DS218play would be a good fit. It will allow you to start with just a single drive and add another one later so you can mirror those drives to each other. Or you can combine capacity and have a twice as big drive, but good backup is recommended.
You use Plex for organizing media and play music on your Sonos (with actual files living on the Synology).
I hope this helps.