Mapman, I'm sorry, but as I said that doesn't make your case. I doubt seriously given my experiences that many pcs are well engineered or as I would prefer, designed. As we know from NASA, neither are rockets perfectly designed and trajectories perfect, or we would not need midcourse corrections.
I don't expect to alter your opinion, and you should not expect to alter mine. I would never argue that a power cord can solve all the problems with unclean power. Maybe Enid Lumley was right a long time ago, when she said we all need to generate our own power off grid.
All I can really say is that I have heard changes on the same component of many different power cords. Their impacts varied greatly. I certainly don't have cheap power cords, but I have seldom heard benefits provided by very expensive power cords to justify their prices.