Selfhosted

If you're considering video transcoding, I'd give Intel a look. Quicksync is pretty well supported across all of the media platforms. I do think Jellyfin is on a much more modern ffmpeg than Plex, and it actually supports AMD. But, I don't have any experience with that... Only Nvidia and Intel. You really don't need a powerful CPU either. I've got my Plex server on a little i5 NUC, and it can do 4k transcodes no problem.

You most likely want graphics for initial install and troubleshooting (like when your NAS loses connection for example). I would recommend a 5600G instead. Nice little APU that works great with Jellyfin transcoding. It's what I have in my own DIY NAS.

You can use the stock cooler it comes with. That's said to be a bit loud so any cheap tower cooler will do. But the 5600 is way overpowered for a home server. And you'd need one with a built in GPU, like the 5600G. While having more power than needed is not a bad thing, this baby will suck quite a bit of electricity so it's more expensive to run. Unless you really need the power, I'd look at an Intel N150 or N200.

People buils jellyfin media servers out nases which have complete garbage computing power. It really does not take much unless you have like 4 4k tvs and fell for dolby atmos scam.

The gold standard for transcoding these days is a newer gen Intel CPU with integrated graphics.

The integrated GPU on those intel chips can do Intel QuickSync / QSV which will handle a dozen streams at once without breaking a sweat.

Dedicated GPUs are obviously going to be more powerful. I've never run ai before so maybe someone else can weigh in on the requirements for it, but I can say for sure that an igpu is good enough for jellyfin transcoding. It also depends on your budget, do you want to spend the extra money just for a dedicated GPU?

If you go igpu route I think that Intel is recommended over AMD, but you should probably do extra research on that before buying

Interesting, why intel?

Also the Node 804 is worth looking into with an entire separate chamber for HDDs in order to keep them cool without exposing them to GPU and cpu heat, plus it is a lot shorter instead, sometimes easier to fit places (mATX motherboard only)

I don't have a ton of experience with other cases but I have been blown away by the quality and customizability of the Define 6. It's super solid with good hardware and the ability to convert it around to different formats. You will need to purchase extra drive caddies as mine only came with 4 I think but I've bought extras over the years to the point that I have an extra set that I didn't realize I had. The whole front is drive space from floor to ceiling and It has two mounts in the back for 2.5" drives along with two in the front that can be used to mount a GPU vertically or for two additional 2.5" drives. You will need to buy two extra 2.5 mounts to use all four spots though. Apart from that it's silent like I mentioned with foam in the top panel to deaden noise. It also has removable screens in the base and front for the air intake to make it easy to clean the dust out. Both side panels are removable with lots of cable management built in and a built-in fan hub.

I'm not super familiar with the 7th gen Define and it's XL counterpart so you may do some research to ensure it has the same capacity if these are all you can find now. The Define 6 is only slightly larger than my old Antec midtower case.

I have a first gen Define XL that's probably closing in on 15 years old. Still going strong as my primary desktop case. The only problem I've had is little cheap plastic connectors to attach the feet to the case broke. I know they've fixed the design for recent versions but I can't justify the cost when the rest still works fine.

Yeah, but even if they seems to be contradictory messages, they are not.

RAM is always the first resource that is depleted is a nas/homeserver built, more ram or the possibility of expanding the ram is always a safe bet. But for a nas or a non Realtime system ddr4 is also not mandatory.

Reduce the cooling goes into the direction that the system is not going to be under high cpu load, so no need to dissipate, you can even reduce the cpu.

SSD is not necessary for a nas but it will make you VMs or containers snappier.

So coming back to the subject, your cpu is overkill, and therefore your mother board too (it has even support for sli!), having more ram is always good but my opinion is with 16gb you are good to go for a good amount of time (my server runs on 8gb and I don't experience any problem yet), obviously, your cooling needs to pair your cpu tdp.

SSD or m2 memories are cheap additions, and like somebody else suggested, it is good to have many pci slots even if they don't go full speed (x16) but will give you the flexibility to add more sata ports or Ethernet connections on the 10gb.

Honestly, if budget is not a concern you can not be mistaken with this built, but I can see potential to spare like 100 bucks in hw and another 100 in bills in next years

Yeh a DAS is basically just an enclosure, well most of them. Some do have hardware raid though.

Is there harm if you continue to use your existing nas just for storage?

Ah, that's a good point. The full tower version has space for that, though.

I'm not saying you should get an Optiplex 7050 specifically, but a used office PC tower (like an Opitplex, HP Elitedesk, Lenovo Thinkcenter, etc) can be picked up for under $500, ready to go, and has more than enough processing power to handle the loads you're asking of it. Plus, they usually have Intel's AMT management option (aka "vPro"), which allows you to remotely manage the PC even when it's powered off.

There are some caveats, but you could always extend your storage capabilities with a USB-DAS. I currently have two with 4 slots each extending a small NUC-style server.

PS: I don't see a mention of at least one SSD. If not already planned, you should at the very least use one for the OS.