I recently did some experimenting on this exact topic. I have some very good DIY cable, solid core copper with silver plating, and have used it throughout my system. I had been using it as the power cord to my Bel Canto CDT-3 transport with the pretty good IeGO 8075 rhodium plated copper AC plugs and thought the sound to be fine. I found a pair of Oyaide 046 plugs that I had stashed and decided to give them a try on this power cord. There was an obvious change in sound, a bit more inner detail, the images took on greater palpability being more specific and more rounded. The change wasn't huge but easily noticeable.
This had me wondering about further improvements by using the Oyaide 004 plugs instead, which are another step up. The 046's are a bit sweet in my opinion. The 004's offer greater detail across the board and greater control. They also are more dynamic and the bass is more textured. Honestly, I think the 004 betters the 046 in just about every way, unless you need the sweetness that the 046's have.
So yes, in my experience, it's well worth it to upgrade your transport power cord as much as you can afford. In a resolving system, just about everything does matter