$300 power cables? How the hell can a metre of highly refined metal make the slightest bit of difference when the rest of the building is connected with ordinary household wiring?
The only way this wank can have any substance at all is when the entire electrical linkage from the generating plant at the powerhouse to the hifi component is connected with identical wiring.
Incidentally, when Monster Cable and similar products first appeared on the Australian market a few years ago, a leading Australian electronics magazine (known for its objectivity) subjected them to double blind testing with ordinary electrical cables of similar sizes. Both audio and electrical tests were conducted, using the best of scientific instrumentation. Despite their best efforts, the tests were unable to discern any difference, either electrically or audibly, between the audiophile cable and the ordinary stuff. So much for the claims of the golden-ears!
(Sorry, no cite on this, but the magazine was called Electronics Australia, and is now defunct).
Digital signals are higher in frequency than audio signals and they are also square waves instead of smoother analog wave forms (square waves have a much higher harmonic frequency content). “Digital” cables will be lower capacitance wire (to handle the higher frequencies involved) and will have better shielding to stop the high frequency noise from the square waves from affecting other equipment.
That said, digital signals can tolerate a much higher degree of signal corruption than analog signals, because a slight degredation of signal is basically ignored. It is only when you get enough degredation in the signal that you actually cause bits to be misread that you have a problem. Add to this the fact that the “other equipment” involved in your stereo system is probably designed to filter off external noise anyway and from a practical standpoint you may not notice any difference between the two cables.