AMD Ryzen 5 5600GT 6-Core 3.6 GHz CPU + 16GB Team T-Force Vulcan Z DDR4 RAM

Depends. If you only need CIFS and/or NFS, this is overkill. A $50 CPU would be enough w/ 8GB of RAM.

However, if you want to do lots of other things, like run VMs, Containers, transcode video so all your old devices can play it, then this wouldn't be a bad thing. Just be certain to get a motherboard with the number and types of storage connections you need. Beware that some motherboards may have 2 m.2 slots, but if you use one of them as an m.2 SATA (for some reason?), then you'll usually lose 2 of the regular SATA ports on the motherboard. With a NAS, you'll want to ensure multiple NICs, preferably Intel NICs which offload more processing than the cheapo alternatives AND NAS distros support Intel NICs better. The NICs matter, if you want to avoid issues.

I've had a NAS at home since around 2000 - always home-built. For years, I used a $100 computer with a slow AMD E-350 APU in an ITX case until I filled up the 4TB HDD. Then I moved to a Pentium G3258 which was a $126 computer and used that until the realtek NIC got flakey. That lead to data corruption, but the CPU was sufficient to run about 4 linux VMs. Used that system for over 5 yrs and got to over 20TB of storage. More and more, my content needed to be transcoded. While the Pentium could do it for non-1080p content, at 1080p, it choked. Replaced it with a Ryzen 5600G which I still have. Also have abuoot 40TB of storage, 32G of RAM, is it running 8 VMs and 10 containers as well. Oh, and it is the LAN backup server, pulling backups from about 8 computers nightly.

Now, if you want ZFS, beware that Ryzen systems that we can build don't actually support ECC RAM. For a NAS inside a business, I wouldn't settle for non-ECC RAM, but at home, ZFS even without ECC RAM is better than the alternatives.

Best of all, the iGPU is more than fast enough and can be used for hardware h.264 and h.265 encoding at about 3x speed, if you use Jellyfin for your media center. The hardware encoding makes larger files and less quality files than, say , handbrake does, so it isn't for long term collecting, but if you have a video you plan to watch just once in a format that your playback devices hate (looking at you google with VP9!), then the real-time transcoding as needed is better than having a player lockup.

What makes this a deal is the RAM is included and that you don't need to buy a GPU. Say the RAM is $40 and the cheapest GPU is 100, you'd be in $140 without a CPU! Seems like a bargain to me. You'll still need a good motherboard. Limiting those to just the ones with Intel NICs will vastly reduce the possible models. With Linux, it is amazing how often the wrong realtek drivers get selected. I think that's because Realtek doesn't change the model even when they completely change the chips used. Intel has some less-great models too, but if you avoid the vXXXX stuff, it tends to "just work".

Oh, and how stable is it? Well, I patched yesterday and there was a new kernel, so I rebooted, but the system is up until I reboot it for patching reasons. There are ways around that too, using LivePatch methods, but I don't mind rebooting about once a month.

At my LUG a few months ago, we helped a new user setup a small 2-disk NAS for their home network on a used Core i3 10th gen off ebay. She didn't know much about Linux or networking and was able to do it herself. The only problem happened when her network was down. After tried a few things, we discovered she'd unplugged the ethernet cable. Could happen to anyone. I've done it. All those cables back there can be confusing.

Whether parts make sense really comes down to whether you have a screwdriver and some old stuff (case, PSU, keyboard, mouse, monitor and disks) to be reused in the "new" system. Some people like to sell their complete old system and there are suckers out there who will pay. I feel guilty selling a 5 yr old MB+RAM+CPU for $50, but lots of people wouldn't.

So,. what do you plan to do with the NAS? That's really the question.

19MB of CPU cache compared to the 32MB in 5600/5600X. Will likely perform worse overall to the normal versions and not a great pickup unless you need the iGPU

Yes, but you would also need a new motherboard and quite possibly new RAM too. At that point, it's worth looking into the 8600G plus motherboard and DDR5 memory. Much more future-proofing (DDR5 plus socket AM5) and somewhat better performance too, especially graphics.