Do components matter? Are some components magic?

THE IDEA THAT COMPONENT SELECTION DOES NOT MATTER IS AS FOOLISH AS THE IDEA THAT COMPONENTS CAN BE MAGIC

While no parts contain magic, changing any given part does change the sound (if only in a very small way or under a certain circumstance). An electronic circuit contains at least a few (and often many) components, all of which have some level of manufacturing tolerance which creates some small (or large) amount of individuality to the final circuit. Each component has many different characteristics, some of which are only important in certain circumstances. Changing only one thing may not result in an easily audible change, but that does not mean it does not matter in the greater context of a complete circuit, a production run of that circuit, or the way that circuit behaves in different circumstances. Also, measuring perceived sound quality is incredibly difficult and the circumstances of use cases incredibly varied. Sadly, what constitutes a relevant change is not a numerical value and may vary with the user and the circumstance.

So in short, sometimes it matters and sometimes it doesn't, and that decision may come all the way down to the user.