[julie_m]

Adequacy is the enemy of perfection. Today's mass-produced amplifiers and speakers can give a performance that would once have been considered excellent. It's not perfectly linear from DC to RF, or even over the full range of human hearing; but it's good enough for most people, most of the time, so that's the way the market moves. Once you pass a certain price point, diminishing returns set in; but even before then, the amplifier and speakers will already be near enough perfect that the listening environment is going to begin to dominate.

The scientist or engineer can prove that there is no measurable difference whether or not a certain expensive gadget is used, but the audiophool can always protest that the instruments being used are simply not sensitive enough.