Perhaps I should have been more specific. I was refuting your claim: "your stereo - no matter how bad - will handily outperform your ears." This is trivially untrue. Another commenter mentions blown speakers as a counterexample. Or if I had to, I could build a set of speakers so terrible only deaf people could tolerate it. So the idea that your ears can't appreciate the difference between ANY pair of competing stereos, "no matter how bad" one of them is, is obviously wrong. We might disagree on where the quality floor is, but we must agree that it exists.