Why do you need 36G of RAM if you are "going to do as little as possible on the machine directly" and it's also a "budget build" from your first post above? I think you may be fine with far less RAM.
Well I felt like a lot of RAM and decent processor would be very helpful when moving very large amounts of data. Plus it's so cheap now a days. A lot of people have 8-16Gb of ram in a nas with pretty low performing CPU. It is budget in a way, I've been buying some stuff used, planning on grabbing a psu, dvdrw, and ssd from a prior unused computer.
The NAS I was looking at getting was a Qnap Ts-453Be which is $500 diskless. So I'm trying to come in under that but with a more capable device. With that budget I need a motherboard/CPU, ram, and case. I actually was *considering* some old Xeon E5 cpu's that you can get refurbished for $100+/- that score 10,000-15,000 on Passmark. But newer motherboards have newer features like hdmi and USB 3.1, etc.
Anyway, the budget is I'm not looking to buy a expensive gaming video card, liquid cooler, etc. But I can spend a little where itll count.