powercords

I certainly have, personally, experienced the improvement power cords can make on amplifiers...how about their value on other items, such as preamps with external powersuppies, and phono preamps....I know better than to apply layperson logic, which doesn't always work in audio, but it would seem that items that draw less "juice" would be less prone to changes in power cords....thoughts welcomed, but experience more interesting to me.....thanks
J