I need to keep power usage in mind and don't want to spend more than 500€ on hardware. Power is roughly 0.35ct/kwh in Germany
I like the small square machines (former NUC). But I don't have any overview which ones are worth the price.
For data storage I am thinking about a NAS, but it would need at least two HDDs for redundancy, otherwise it's not better than an external HDD that I have. Also it does have its own power draw, which isn't insignificant (10w->~300€/10years).
Capabilities of the machine don't matter too much, I will see what I can do with the hardware I get.
Is there a sweet spot, a device that everyone buys or cheapest brand or best package or whatever?
There are some nice NAS focussed mini-itx boards with integrated CPU and cooling (usually Intel N150 or similar) that fit well into small media PC cases.
That is a bit bigger than a NUC, but you can fit hard drives easily and these mainboards usually have a lot of extension ports and multiple on board m2 slots for NVMe discs.
Where do I find them though?
Alibaba and the like, although I think there are also resellers on Amazon etc.
Really? I don't know if I feel comfortable spending that much money on aliexpress. Aren't there EU stores that stock this stuff? And reputable brands?
ASrock has a few similar mini-itx boards with passive cooled CPUs soldered on, but they are not nearly as fully featured as what some of the Chinese brands sell.