Where are the low-watt server motherboards of yester year?

I'm looking for a new motherboard to put in a place with cheap bandwidth and very expensive power. Peak use must stay below 30 watts, including 2 2.5 SSDs. I also need 16+ G of ram, serial console, and want to stay below $US 400. This used to be easy, but now seems impossible.
In the past I used mini-itx motherboards with a built in atom or celeron J and 2-4 SATA ports that I used with a mix of SSDs and 2.5" drives. There doesn't seem to be a modern equivalent. Everything I find is 0) built 2+ years ago, 1) much faster/higher watt, 2) an embedded board with only 1 SATA port that would need to be shoehorned into a 1U , or 3) a desktop board that doesn't expect front to back ventilation like you would find in a 1U server in a hot rack, 4) any of the above, with no built in serial.

Intel Nics would be nice. I occasionally need to run an app that requires openGL, so onboard video is good but not essential.

I've looked into Arm motherboards, but worry that updating the boot process or firmware may be more experimental and exciting than x86. Raspberry pi maker boards don't have enough RAM.

Is my best bet going to ebay & finding something old & good enough?