Cheapest Motherboard/CPU Combo with support for ECC?

[oguruma]

I'd like to build a small and cheap NAS to act as an off-site backup of my main NAS. I'll only need about 40TB of useable storage.

I'd like a motherboard/CPU combo that:
1) can be purchased new
2) supports ECC RAM
3) is Mini-ITX or Micro ATX
4) doesn't generate a lot of heat
5) is "affordable"

 

[Patrick M. Hausen]

"Look for Supermicro A2SDi series or comparable ASrock and don't shy away from buying used" would be my recommendation.

Your requirements are sane and perfectly in line with what I would buy (and actually did buy) myself but all of this screams "server/enterprise grade" and they charge a premium because they can. So instead of going for cheaper consumer grade products I would reconsider buying used/refurbished.

I was in the lucky situation that I positively decided to invest into a new Xeon D based NAS, so suddenly I had my old Atom based one available as the backup system. Similarly I bought a Xeon D Supermicro board for my ESXi + TN SCALE and there was another Atom based system waiting to get OPNsense installed ...

Depending on where you are located I am a satisfied customer of Jacob (german) and Tonitrus (international) who both offer used products - with varying availability, of course.