Is the best power cord no power cord at all?

Can anyone point me to a thread providing possible explanations as to why power cords can make such an important improvement in sound?

My friend is a tinkerer, and his theory is that reducing or eliminating RF is crucial for high fidelity, and that this is something that a well-constructed power cord can do. He says that Marigo power cords are designed to address RF, and there is no question that they have improved the sound of my amplifiers to a very material degree.

To take this idea one step further: My friend has also designed a preamp, a separate phono stage and a mod for the analog portion of an off-the-shelf cd player, each running on a separate DC power supply that has sufficient storage capacity to run these components with the power cord completely disconnected. Ie, stock power cords are hooked up to the batteries to charge the batteries when the system is not being played, but is then disconnected when the system is playing music. Playback time on battery power is in the range of 8-12 hours.

The batteries are large and expensive, but no more expensive than a high-grade power cord, which can be done without in this sort of system. And my system does play beautifully, with a noticeable improvement in the sound when the power cord is disconnected. His explanation, again, is the elimination of RF.

Any thoughts as to (i) whether reduction/elimination of RF is the source of improvement and (ii) whether this type of power-cord-less set-up could be incorporated into commercially available components?