40 cores of Xeon E5-2680

So there are your power whores. TDP 4 x 115 W. But they are old and very poor…

my load average is less than 1

… because nobody ever comes to visit them. Kindly give them the boot.

my knowledge of desktop technology

No worries. You don’t need to go that far :) At least don’t touch things that have “Gaming” as their firstname. Just look for some (nearly) modern CPU(s) because they are so much more power efficient, and spend some hours at www.cpubenchmark.net

An example from the other end: my current server runs an Intel G4560T (35W). My next server will get 1 or 2 Ryzen 5825U’s (15W each).