I bought a couple of Odroid HC4. I boot from a microSD. I can plug my old SATA disks in there. The board with an old 750 HDD consumes 12 to 15 W. If I unmount the HDD file system and switch off the disk with udisksctl power-off it's only 4 W. Any operation on the device turns the disk on again. I'll check with a spare SSD.

Even if I had a different use case Pis are impossible to find at a price worth paying for. I'm starting to forget about them.