I would like to apologize for my previous post. In it I said that with a good cable you can hear how horrible MP3s sound, but in fact MP3s become much more tolerable.
My Zu Pivot connected to my PowerBook made it possible to hear how compressed my MP3s were, it's true. They are truly lifeless things, relatively speaking. But the improvements in warmth, dimension and detail were there too.
I am sorry that, for the sake of taking a swipe at an easy target like MP3s, I gave the impression that I thought a poor recording made good equipment pointless. I do not believe this. Good gear makes everything much more listenable, in my experience.