The Xeon D's are nice (8 physical / 16 logical cores for less than 45W for the D-1541) but I wouldn't recommend buying Supermicro's pre-assembled machines for home lab use; they are noisy. It would be better to buy their bare motherboards instead (e.g. http://www.supermicro.com/products/motherboard/Xeon/D/X10SDV...) and self-install it into a low-noise mini-ITX case instead.

How loud is that little Supermicro, though?

Yeah definitely noisier. https://tinkertry.com/supermicro-superserver-sys-e200-8d-and... shows about 60db(!) with fans at full blast during spinup but 42db or so when dialled down. So not too bad.

The difference with IPMI tho is you can safely put them in the attic or wherever.