NAS is network attached storage, basically a small computer with an Ethernet or WiFi connection to your local network and a hard drive for storage.

Your PC should be able to store and share your music under Windows but you’ll have to leave the computer on to play it.

Before spending any money wait for a Sonos issue to occur, submit a diagnostic within a few minutes then post the number and problem here or use one of the other Sonos support options to get them to look at it.

Regardless I am going to have to buy a new computer/PC. I would like to avoid leaving my computer on 24/7. So doing a little more research on NAS, I could purchase one right now (WD My Cloud appr $180) and use that till I figure out which PC to get.
My router is located upstairs in one of our bedrooms and my MAC is in our master bedroom (upstairs). I would like to keep the NAS in our master bedroom alongside the MAC. Do I need to run Ethernet cable from the NAS to router? Or do I use WiFi to connect to router? Asking because I already have Ethernet running from router to MAC. I would have to purchase a switch for both MAC & NAS to avoid running more Ethernet to from room to room. Once the NAS is connected and all files stored inside I should be able to run Sonos straight from NAS? How do I get all my iTunes from my MAC to NAS? I have probably over 40,000 songs in my MAC. And once all my iTunes are in NAS can I delete them from my MAC to free up storage? Sorry for all the questions. All this is new for me. Just trying to figure out the best way to use my Sonos without relying on my MAC.

Wired or WiFi depends on your NAS, I prefer wired for reliability and speed but either will work for Sonos. You can get a good Ethernet Switch for around $20, check the Sonos incompatible hardware list first.

The WD should work, you just need to make sure that SMB v1 (not just v2 or v3) is enabled or Sonos won’t connect to it.

You will still run Sonos from your computer, phone or tablet, just as you do now. All that will be on the NAS is your music collection.

You should be able to connect your Mac to the NAS over the network and use your normal file copy tool to copy the files. I do recommend keeping a backup copy on a second device.

Once the files are copied just open your Sonos Controller and move the music library from your old (Mac) location to the new NAS location and let it re-index.

So I need to leave my music file on my MAC/computer. Am I able to turn off my computer and use my Sonos through NAS? I will get a external hard drive to back up my files. Can you recommend a NAS please? From what I’ve read here so far the WD has some mixed reviews. 

You do not need your computer running if your music is on the NAS. The only thing your computer would be doing at that point is to run the Sonos Controller if you wanted to use it from there.

I can’t recommend a NAS, but I share your reservations about the WD units. I have one that they abandoned support for so it is unsafe to connect to the network rendering it useless.

Personally I use a Raspberry Pi for my Sonos NAS but that does require a bit of Linux skill and tweaking to get going. I’ve heard good things about Buffalo, Synology, QNAP and TerraMaster, all of which are more than needed to support your Sonos.

I’d search here for NAS and see what others have said in the past.