@vetsc5 I like the article you referenced and have three comments.
1. Just about everybody assumes that exotic power cables fix up the power coming from the wall. Why that last six feet has that effect is beyond me. Instead, I would suggest that power cables may reduce noise coming from your own components!
2. The article was written some time ago, when transformers were near ubiquitous. Now we have switch-mode or switching power supplies in many components. Switch mode works from the high voltage spike produced when you suddenly switch off current. Class D amplifiers use this principle. A high frequency chopped square-wave contains lots of very high frequency harmonics!
3. I have personal, objective, repeatable evidence of the dramatic effect changing a power cord can have on a digital source. I live in a marginal reception area for digital TV and have a small motorhome with a domestic AV stack. The TV aerial is on the roof above the stack, and a powered KEF Class D subwoofer is at the bottom. TV reception is perfect until the subwoofer is switched on, which totally annihilates the picture. The solution, as mentioned in your article, is a couple of cheap ferrites clamped around the subwoofer's power cord. What is happening is that the Class D amplifier in the KEF in injecting high frequency electrical noise into the power cable. The obvious effect is interference with low-level broadcast digital signals, but equally this noise is injected into other components on the same circuit.