What About Loom Theory?

Nordost is one company that promotes this philosophy in regards to selecting cables for a system. You can see their explanation for it in their document entitled Foundation Theory, under the section heading "Interconnects and Speaker Cables". They say that it applies to power cables as well, and they also state that a more expensive cable is not always better in specific applications.

The original poster asked for an explanation of what loom theory was, so I provided the only documented source that I know of where it is explained. I'm not promoting it or saying that it's the answer for everyone, just trying to answer the poster's question.