Look at used passive cooled stuff with mobile CPUs! I have 2 boxes with i3-7100u CPUs, 32GB RAM, and a proper SATA SSD that use around 2W of power each most of

Look at used passive cooled stuff with mobile CPUs! I have 2 boxes with i3-7100u CPUs, 32GB RAM, and a proper SATA SSD that use around 2W of power each most of the time. The peak power is of course higher than a Pi, but they generally are near-idle most of the time.