I think they do make a small difference, because stock power cords ARE REALLY crappy and do not provide consistent power. However, to those who think that it is the biggest upgrade in your system well that is simply not realistic or possible. A good power cord with hospital grade plugs will provide all the additional benefit you are going to get. In the case of an amp, it will provide slightly more power to the amp which allows you to reduce to the volume for the same sound pressure which allows the amp to be more effecient and sound better
