Small NAS home server woes

So, I currently have a Netgear ReadyNAS 314 with 1 SSD, 3 HDDs, Intel Atom D2701 and 4GB RAM, running Debian 12, and since getting it I've been getting more into self hosting. What I have now is primarily too weak in the CPU and RAM department, but it could also use more HDDs. I'm aiming for 5-6 3.5 HDDs, 1 Nvme, 1 2.5" SSD.

What I'm currently running:

• Samba and NFS server

• OpenVPN

• Jellyseerr/Jellyfin/*arr stack

• Pangolin

• Dawarich

• Immich

• rsnapshot

• Homepage

And it's rather sluggish right now, and is almost filling up its 4GB of swap.

What I'd also like to be able to run/have:

• Nextcloud

• Transcoding (including ability to decode AV1, but preferably also encode)

• Anything else I may want to run (working on degoogling myself)

• ECC RAM (to prevent bitrot, I'm already running btrfs raid1 to prevent bitrot from faulty disks)

• 1x 2.5G ethernet

If possible I'd like to have some room for upgradeability. I'm aiming for a low power build, that should be rather compact, especially not very wide unless I can find a better place in my office for it.

I'm looking at a Jonsbo N1 chassis (17cm wide) , but I'm also following a Readynas 626 (19cm wide) in an online auction. Options:

Intel N100 board

Pros: cheap, low power, quicksync with av1 decode

Cons: boards with 2.5G ethernet have to be ordered from Aliexpress and have no support and uses the JMB585 chip that prevents low power C states, limited pcie lanes, no AV1 encode, not very upgradeable (1 DIMM, soldered CPU) , no ECC, I worry it may be too slow

Intel 13100

Pros: AV1 decode, quite fast, upgradeable

Cons: No ECC, relatively expensive, no AV1 encode

AMD 8500G

Pros: AV1 enc/dec, ECC, relatively fast, upgradeable

Cons: relatively expensive, not as low power as the 13100

Readynas 626

Pros: enterprise grade HW, less DIY, ECC, may be relatively cheap

Cons: high power for its performance (roughly that of the N100), wider (19cm) than a Jonsbo N1 (17cm), not upgradeable (no CPU or mobo swap), expensive DDR4 2133 ECC UDIMM, doesn't have M.2 but has a PCIE slot

I'd love to hear what you think about these options and whether you have other concerns that I haven't thought about.

Edit: I just now realized that the 13100 doesn't have AV1 encode in HW, that didn't come until Core Ultra. And wowee, suitable mITX mobos start at 400$ here! I think AMD is the realistic choice if I want to go for AV1 HW encode...