@sanityinc I'm no hardware expert but I'd probably buy a cheap ThinkCentre on the 2nd hand market. Should be #energy efficient and has enough power for your use-cases IMO. Costs probably ~100-150€.
I personally switched from #RAID(5) to one single very large HDD over 15 years ago (currently 16TB). It's less complex, cheaper and consumes less energy.
Currently, I do have a basically noise-less i5 in a cool mini tower which has an idle consumption of <20W which runs 24/7 using #Debian stable.
My components (from early 2023): https://geizhals.at/wishlists/2985583 Most components are from a #heise DIY-article from 2022-11 or so.
I use it as my personal #workstation as well as a #NAS as well as our home server. I've never owned a better computer so far and I'll never switch back to 1-litre-computers anymore (e.g., intel #NUC).