I agree that changing a single component in a system may, although not necessarily, noticeably alter the sound. For my first post-college system, I visited stereo stores in Anchorage. (During the pipeline construction years, lots of folks had some extra bucks, and there were several audio stores.) I couldn’t afford what I really wanted, but bought a Garrard turntable, an Onkyo receiver, and ADS 710L speakers. Being a buy-and-hold kind of guy, only several years later did I swap out the Onkyo for an Adcom integrated. The improvement was significant. More than several years later and after adding a Sony ES disc player, I traded the ADS speakers for Harbeth M30s (which I still use daily). Again, great improvement. Then I traded the Adcom for a Classe, even better yet. Then the Classe went kaput, and I bought a wyred4sound integrated, which I think is the best so far.
Now, I heard improvements but my choices haven’t been true high-end. But they have given my wife and I decades of pleasure. And I’ve enjoyed the process of making changes when I have. My hearing has diminished, and I don’t know whether my approach would give satisfactory results, given higher costs for audio equipment, especially speakers, which in theory are due for an upgrade.