Power cable influences on equipment has to do with a) less contact resistance b) less rfi and emi pick-up, and transfer to the component c) less cross-contamination from components on nearby other components and cables d) less voltage drop e) less (lower) leakage currents and parasitic capacitance between components.f) quicker rise times/faster current draw.
But, if the incoming electricity is dirty the effect will be reduced offcourse,
Sometimes changing one power cable can have an effect on other equipment in your system.You only hear the endresult. A lot of people have heard the change a good power cable can bring to your system. Who I am to judge? If you don't hear it, be happy and listen to some good music.
Love to hear other peoples experiences. 'Facts', 'Engineering' and 'Measurments'. can be discussed in Tech Talk.