[sajunky]

Getting the system as quiet as possible is always advisable, but it doesn't always pay off. For instance if you have a tube amplifier that sounds gorgeous, you probably have a higher noise floor and you won't notice the improvement. Same goes for the speakers/headphones and sensitivity. And amplifiers and their resolution and resolving power or speakers with complex filters.

I agree, but a noise we are talking about do not contribute to a higher noise floor like in the analogue gear. Distortions are added proportionally to a music, nothing is heard when music get silent. An untrained ear don't recognise these distortions, we only start to understand what was wrong when distortions go away.