OK, Scot
If you consider the noise floor than I can tell that it 99.99999% depend on ELECTRONICS and the rest on wires(as long as they have tight well-soldered or crimped connectors). By acquiring wires with "lower noise floor" or "black background wires" it's meant that lacking one-over-a-hundred-thousand-th fracture for what you're going to pay up a price of nice diamond ring that looks much better visually:-)
Electronics are to be created and designed with influence of wires or allowed tolerance of wire load(that's why different wires act certainly different on components but not to the crazy degree of some "noise reduction").
Electronics that are sencitive to wires and "like" expencive ones such as Valhalla or Nirvana stuff meant to be designed with super-conductive wires(I scientifically assume) i.e. with zero impedance at any length.
To some point designers of audio components sacrifice the noise canceling for the shorter and more transperent signal path. In this case the solution to the reducing noise floor is using less-sencitive(efficient) speakers and possibly power conditioners. MIT wires are also can be a cost-effective solution(with noise canceling networks) in that case(except mega-priced ones) but that also reduces transperency that had been originally meant.
As to actively shielded ones how many outlets extra you're going to need if you use them? It seems by killing RF you're waking up more AC(if applicable)