curiousjm:
This one's easy, and I think many of the posters have implied the same thing. If you replace a component with an ostensibly better component, but don't hear a difference, there's one obvious conclusion: The component you replaced wasn't the weakest link in the signal chain. And when we say "signal chain," we have to include your ears and your acoustic environment.
I've replaced some cables and heard absolutely no difference. Others have made a huge difference. When I replaced all the power cables with good, mid-priced Audioquest cables and simultaneously added an AudioQuest Niagara power conditioner, I experienced what was arguably the most dramatic improvement in sound I've heard in, jeez, 20 years. That was because my AC mains -- driven by characteristically noisy rooftop solar panels -- was my weakest link.