We compared a few different power cords at a recent NY Rave meeting. A KS cord was there and it easily bested the bunch on both the amp and the DAC. Definitely the nicest sounding power cord I've ever heard, and I've listened to a few. Pricey, but if you've got the cash and want the best ...
Yes, power cords definitely act as tone controls, so what works best in one situation may sound different in another. Don't you just hate this trial and error stuff when the costs are so high?
Enjoy,
Bob