I have chromebox (with 32GB DDR4) that idle at 4W, but after adding couple nvme drives it doubled it's power consumption. Having full ATX mobo is cool (flexibility), with BIOS settings, powertop, and some other settings can also idle at quite low power. I have i7-7700K that idle at 18W. With combination of wake-on-lan and similar you can have a monster but won't empty your wallet.