What is an excellent power cable?

An excellent power cable is any that is capable of conducting sufficient electricity to your component. 

That's one thing you find out.   Ask a question.   Come away knowing less
Then you started Out knowing.    There all good or bad.  It depends on how thay play togather with the system you have 

Consider new outlets too. I have the standard 15 amp circuits in my living room . I upgraded the 2  outlets to Hubbell . When I replaced some outlets in other areas of the house , I noticed that the connectors were a cheaply made push in spring ( no tension screw). List price on 2 Hubbell outlets is about $90. They have beefy screw connectors and grip my power cords extremely well . And like everything Audio , take time to settle in . Alao be advised that mine are 20 amp outlets on a 15 rated wire and breaker . So I only use 15 amp cords . Many people here have gone to dedicated 20 amp circuits , but that’s above my level at this time . So it’s my room and my gear , so it’s a hazard free situation . If I move I’ll put some 15’s in and take them with me . But to think that my entire system was powered through 2 outlets that cost about $0.75 ea and I’m pushing $10k in gear was an easy choice . So look at the reviews and pick a price point and change your outlets. My experience is that this will compliment what you are striving too achieve. I would also like to comment on the well founded recommendations and the politeness demonstrated  in this thread . Happy Listening , Mike B. 

  More ramblings . +1 to Mofimadness on the Signal Cable Magic Power Cable. I’m running one on my Schiit Yiggy and I agree with him . On power conditioning Vs distribution , I chose the Richard Gray 600. It has six outlets and a quality cord . It uses a “ PARALELL CHOKE “ method . So being in parallel and having large capatance, it does not restrict current flow . You can turn it off and your equipment is still powered ( my Yiggy stays powered 24/7 ). I turn off my pre and power amp as I’m running NOS tubes . I’m running 96db speakers and it’s more then subtle when I introduce changes . I like the Gray very much and yes I did try “ Straight into the Hubble outlets “.

ostensible_constituency

An excellent power cable is any that is capable of conducting sufficient electricity to your component.

You've confused competence with excellence.