When you're going to construct a tall building you first need to dig down to bedrock to can anchor its foundation.
The same can be said for building a high performance music system. Without firm foundations decisions we make in building materials are suspect.
Take for example cables: the nails we use to bind the building parts together. Cables are typically chosen for their synergistic contributions to the overall sound, yet often, they're used as a crutch to prop up a weak foundation.
Imagine you built your system without consideration of proper power conditioning, taking whatever the wall AC gives you. You'd be faced with weaker bass, dirty, grungy, upper harmonic structure to the music. The cables you subsequently choose would likely try to compensate for the failings of the power. You'd find cables that rolled off the upper end, thus reinforcing the lower regions and obfuscating the grunge.
Then one day you decide to fix the AC power. Now your system seems bass heavy, duller, out of whack.
If you have the luxury of starting fresh, make sure you check with your architect first.
It takes some digging to reach bedrock, but once anchored, the rest gets easy.