Many audiophiles (myself included) consistently focus on earth grounds, grounding, and "clean" power. Yes, that's important, to maintain low noise floors (as earth grounds can also act as bonding conductors, which is also good), but what many times gets overlooked (IMO) are AC neutrals. Many times you can lower AC power total harmonic distortion (THD) by maintaining clean neutrals (and sometimes even oversizing them).
Let's take for example a dedicated 20 amp circuit, exclusively used for audio equipment. If you only plugged in one piece of audio equipment to that circuit, the THD on that circuit would probably be at 1% or lower (a good sign of clean power). Start plugging in more equipment to that "dedicated" circuit (especially equipment with switching power supplies), and the THD on that circuit is almost guaranteed to rise in value. The *neutral* bears the burden of equipment with poor power factors. There is a whole science behind this.
When electrical building engineers design an electrical system for a building, (if they're smart) neutrals, and balancing 3 phase electrical systems, are paid close attention to (neutrals especially). The story revolving around The First Interstate Tower (now called the Aon Center) fire in 1988 in Los Angeles has many times been reported as electrically related. Here's what Wikipedia says about that: "The fire's origin has been attributed to overloading of the building's electrical system by reactive distortion of lighting circuit currents." I'm not sure reactive current was fully understood in 1988, as computers were just starting to be the norm in office buildings, along with electronic fluorescent ballasts. It is rumored that the building had a lot of personal computers in the building, which all had switching power supplies (along with the numerous electronic fluorescent ballasts), which possibly/probably overloaded undersized neutrals (probably because the 3 phase power was not balanced correctly).
Times have changed, and switching power supplies are being built with better designs these days (energy star), and have better power factors (a perfect power factor is 1.0 or 100%). A perfect power factor means the piece of equipment is using all of its power, efficiently. There are however still a lot of switching power supplies (and electronic ballast fluorescent lighting) out there that have poor power factors, and high THD.
So when establishing (utility powered) AC circuits for audio, have as many dedicated AC circuits as you can, and make sure that each circuit has a dedicated neutral, along with a dedicated isolated ground (no daisy chaining neutrals). I realize this can be costly, and quickly fill up a circuit breaker panel (technical term being Load Center), but it will keep AC circuit THD at low levels, which is the key to maintaining high quality noise free utility AC power.
Personally, besides trying to keep my neutrals clean, I also employ Equitech balanced AC power (Google that), isolation transformers, and Tripp Lite Ultra Isobar surge protectors to keep my noise floors as low as they can be. Good luck everyone.