In my experience, power cord change at the source makes the biggest difference. I started out with my dac and the difference was huge. Then I changed the power cord on the amp, and there were noticeable differences, but not as big as the dac.
Power cord replacement suggestions
If i were to delve into the fanatic behavior of replacing power cords, is there some concensus on where the most impact would be gained, whether on source, pre, or amp, or is it just different for every system and need to experiment. Thanks for any advice.