+1 Boxcarman hit the nail on the head. You can upgrade to any power cord you wish, but you need to get the best power to the cable that you can. I'm not going to discuss power conditioners, as that is not what I am referring to.
I used several power cables in the $300 to $700 range new and used, and heard subtle improvements. I found a thread here that was talking about dedicated lines, power receptacles, etc. I decided to try some of this to see if it was real or snake oil; anyways it couldn't hurt.
I had two dedicated lines installed for about $400, one for the power amps, and one for the signal components.....and that was more of an improvement than any cord I installed.
Then I tested and upgraded the power receptacles, and WOW now we're talking. There was an even bigger improvement. Not only that, but now I could hear the difference between cables and could decide which ones provided improvements.
I tried about 11 or 12 (can't remember exactly) power receptacles over several months from Furutech, Acme, Oyaide, Cardas, Leviton, Hubbell, PS Audio, and Synergistic Research. All made at least some improvement, and others provided great improvements. Here are some thoughts
The Acme receptacle which is heavy silver over high copper brass/cryo treated/CFC treated, is much better than any base or hospital grade I tried (and a couple of the audiophile models listed above)....and well worth the $55 each. Great option for those on a tight budget.
The cream of the crop (and what I currently have installed): Furutech GTX-D(G) gold plated, Furutech GTX-D(R) rhodium plated, and the Oyaide R1 (not the SWO-XX series). My personal favorites in my system are the Furutech GTX-(G) and the Oyaide R1, but I can see how the GTX-D(R) would be preferred by those looking for more detail that they have in spades.....too much in my system, but by some accounts the the rhodium need over 200 hours to break in.
The Furutechs and Oyaide are list price between $200 to $260, but I found the GTX-D(G) and R1 for about $130 on sale, and the GTX-D(R) for $170
Your mileage may vary, but for less than the cost of a new cable, pulling dedicated lines and upgrading the receptacles provided a very noticeable improvement. It also allows me to hear the differences in cables, that I couldn't before.