the magnitude of changes should probably be neglectable especially vs. the investment. if there's better power supply for the motor for example, the magnitude will be much greater. with stock pc you can 'juggle' between outlet and conditioner or even connect it together with any transformer next to each other, connect it to varactor with decreased or increased voltage by 10% and see the effect. if the effect is minimal or barely audible, than you can figure out if it's realy worth to spend $$$ for aftermarket cord.