Power cords can definitely make a difference, however if you don't have a dedicated line/lines and upgraded AC outlet, I would do this first.
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The typical wall outlet is on a circuit with other outlets and possibly lights. A licensed electrician would install a dedicated line by adding a breaker to the box, running wire from that breaker straight to an upgraded wall outlet with no connections in between. It's a good idea to do at least 2 with breakers on the same side of the box. IMO, I would use 20 amp breakers, 10 gauge wire, and 20 amp outlets, but not hospital grade, as these are usually plated.
Here's a good article about the benefits,
As the article states, it is very cost effective for the improvement in sound quality.