“A chain is only as strong as its weakest link” everybody knows, and indeed it applies across many domains, form actual metal chains to security1). But it doesn't really apply well to HiFi, that is the full chain from source to your ears.
Pick your favorite song and imagine you have a perfectly decent recording of it on a CD.
Now your first setup consists of:
Player: a semi-broken crappy knock-off, which requires description:
So it works, technically… you put the CD in and… Well the 502) Hz buzz is constant, and the player doesn't really start outputting anything below 200 Hz. The mids get through and surprisingly, they do have a nice flat reproduction. And then you get above 5 kHz and stuff gets very unpleasant: seemingly random spikes, constant hiss, and during the quiet sections you seem to notice white-noise too. Yes, this is a really crappy player.
Amplifier: a decent one; reproduces 10 - 20k Hz without any shame
Speakers: also decent, but this time a set; 50 - 10k Hz, power rated adequately to the
So what do you get? A room full of noise where you don't really want to be. Everything shakes, the high-pitched noise is painful, and your favorite song is just lost in this misery.
So is this chain as bad as it's weakest link, the
Player? No, it's actually worse as a whole. And to see that…
Now your second setup consists of:
Player: the same! as crappy as ever
Amplifier: well it's there built-in into your mediocre boombox; sanely engineered so it has a strong band-pass filter for 500 Hz - 5 Khz
Speakers: they're built-in too, and matched to the 2x2W of actual3) output power
So what do you get? Your song! It's noticeably cut-off at both ends, but what you hear is listenable, more even, enjoyable if you treat it as background music and get your mind onto other things. It works. The two other components are now objectively worse than the ones from the first setup, and yet your overall experience is much better now. See?