What components are a good value in used market?

Not to be flippant, but any & all of them.

naim audio components hold their value well,sound great and
are supported by the company totally.

Not to support flippancy, but Driver basically correct. Buying on the used market becomes an art. Part of it is timing and part is research. Forums like this, audioreview.com, friends and exposure to various components all come into play. I live in remote Montana so listening before I buy is a challenge. There is 1 high-end dealer here and a couple of chain stores. I rely on internet info and I use the phone extensively ( I'm pretty good at distinguishing between manufacturers who are honest and helpful and those who are just full of themselves and thier products). Just like everyone else, I've bought products I thought were a good deal only to find out it wasn't really what I hoping for. Look around, ask around and DO YOUR HOMEWORK before you buy. Good luck.