In the early days it was always fun to understand the difference between Arc Ref 3 vs Arc Ref 5, 5 vs 5SE, and so on till you get to the top of a brand. Compare it to other similar tubed brands, e.g. VTL, CJ. Then to SS. Similarly with other parts of the chain, like comparing carts or tables with the same cart etc is fun. Or dacs.
However I don't understand how one can evaluate gear without using the musical message. And that's why some people focus on hearing a bit more top, bit more bottom, etc while both components might be screwing up the realism equally. And if they both let through the musically message equally well, the differences might not really matter unless significant. And then the system philosophy matters more.
And the final goal is to get to a system that lets you just hear different performances/concerts.