It's interesting to read how we arrive at our beliefs about cables, outlets, wiring, cords, conditioners. We are usually confident in our decisions in having purchased better amps, speakers, players, etc, because we easily hear the improvements. We are convinced empirically, that is, not by prior knowledge, but by experience and observation. We did not have to be electrical engineers to hear and enjoy those improvements. But the cable and cord naysayers throw up this wall of defense by insisting on bench measurements that are quantifiable, when most of us base our audio opinions on qualitative measurements-- on what we experience.
With that said, here are my findings over 12 years of listening to several levels of gear in the same room. Dealing with the AC power supply that comes into your home is an absolute necessity. That current is unstable and noisy for audio/visual purposes. It is fine for your air conditioner, furnace, washer and dryer, range and garage door opener, ceiling fans and the dozens of other plug-ins you have. But all of those devices and appliances cause voltage drops and switching noise in your circuits, so a dedicated circuit for your system is paramount, and it should be robust, preferably 240 volts in terms of the North American, 120 volt standard. Then one needs a stand-alone product, such as a Torus or Richard Gray isolation transformer that plugs into that 240v receptacle and converts back to 120V. I only mention these based on my experience and because Torus is endorsed/used by Bryston, and my dealer here only offers "best in class" products, including Richard Gray and Bryston. Now you have your own private, plentiful power supply that is stable and protected against surge. This a fundamental requirement in high-end audio/visual. Amps and other high-demand components plug directly into the transformer. You also must further remove noise from your front-end equipment with a large conditioner designed to serve those pre-amps turntables, players, dacs, TVs, and computers. I happen to use a Richard Gray 1200, again plugged directly into a 240/120V transformer. Torus appears to offers all-in-one models that both isolate and condition--I have not tried them--cannot speak from experience there--someone please verify.
Forget about cheap power strips and conditioning receptacles and cryogenics, lamp cord, stock speaker cable sold by the foot. Power cords should be large. Cable terminations should be soldered and have generous, large, gold spades or pins--lots of contact surface there. Interconnects should be balanced for further noise rejection. Speaker cables must be overbuilt, well-insulated. Any cheap cable or interconnect between any of your components is at some point going to be of a length to act as an antenna for some segment of the transmission band. You can count on that. No part of your system should be ordinary, Ok? Unless you are a DIYer, you have to spend some money on these things, sorry to say. If you want a BMW or an Audi, you have to buy one. If you want to truly take high-end to its potential, you must attend to these less glorious, but fundamental rules. I don't want to come off as a snob or a know-it-all--what I know is what I have learned through experience and by listening to my high-end retailer, who has offered and auditioned much of the finest gear made over the past 30 years. (And I drive a Saturn.)