The Synology End Game

On that very topic, do HNers have any case and/or motherboard recommendations for a homebrew NAS?

I have my NAS on a shelf in a mini-ITX case, but it only fits two 3.5" HDDs internally (as well as an SSD, but full-size HDDs are what matter for bulk data storage, the more the better)

Also, it takes a normal full-size ATX PSU because I was fed up a previous case that only had room for its own custom PSU, which kept failing under load. But I note there are now standardised small sizes like TFX12V and LFX12V, are there any efficient and reliable PSUs in these form factors?

I use samba on Debian Linux running on a Mac Mini. The data partition lives on an externally connected Samsung SSD. It's probably not what you want, but it sure is small.