Theoretically, what would be the most power efficient way to run the HL15's backplane?

HBA’s use a lot of power & have inconsistent sleep state support depending on your system. I’m wondering if it makes sense to use a motherboard with 4 or 8 sata cables & use those for 25-50% of the backplane & then use a cheap sata pcie expander card to add the other 50-75% of the connection. You could even use an m.2 to sata converter. You might get some latency penalties by going through the chipset, but I don’t think that would be too much of a problem when only using hard drives. What’s the most power efficient HBA that would work with the backplane?

I believe the Full Build is wiring the backplane into the X11-generation board from Supermicro rather than eating a PCIe slot for a separate HBA, however, I can’t see how the X11 board is going to be dramatically more efficient to run a controller on the mainboard vs. a HBA in the PCIe slot?

I should have specified that I meant standard issue, off the shelf motherboards without the supermicro special features.