I say this everytime SBC's come up: ODroid H2's (1) They're not cheap - about $250 kitted out with 16G RAM and a cheap 250G SSD/M2. But you get full 64 bit linux/windows, dual ethernet, a nice selection of IO ports. And all the low power/small form factor goodness. Bonus - fanless and totally silent when used with SSD.

1: https://ameridroid.com/products/odroid-h2

How would you power and cool such a beast? What kind of workloads would benefit from that much RAM while running happily on a CPU that fits on a typical SBC layout?

If you want a tiny workstation-class system, there are entirely decent mini ITX board you can stuff a recent AMD or Intel chip and tons of RAM into. You'll need a desktop-class cooling system and power supply, though, and it'll still have the footprint of 6-8 of these board, and probably about 15x the total volume and power consumption.

Sounds like you'd want something more like this[1].

[1]: http://www.biostar-usa.com/app/en-us/mb/introduction.php?S_I...