But if I have a system that is considerably better than yours yet cost considerably less, doesn't need the same money again spent on mains leads or other wires, or secret sect 'modifications' just plugs into the wall and works, who's the muppet?

FWIW if a component is radiating down its mains lead such that a special cable is required to suppress it, or is susceptible to interference picked up on its mains cable, then it is poorly engineered and quite possibly not CE compliant. At the very least it should be supplied with a suitable mains lead. And, regardless, screened mains cable doesn't cost that much. £2 a metre for well over the top stuff from RS for example.

Paul