For those wondering...in SPL they're attempting to extract EVERY BIT of volume from their system. It can become very involved. At the heart of all this is your gain. The goal is to maximize the playback potential from start to finish. The gain bridges the source to the amplifiers. Everything else is a domino effect. What Fatboy and the other are saying, nm...it just begs the question of whether or not it's applicable to the op's application and needs.
Majority of daily drivers set the gain and leave it. Apparently these two guys take everything a step farther. You're playing with fire when you do that; as they've previously stated.
Anyways...here's a quick fyi on gain and how it applies to the system. Unregulated power supplies certainly make it a circus act when attempting to balance everything and maintain harmony.
Amplifier Gain Controls