Power Cords


I currently have Wireworld Silver Electra power cords with upgraded Platinum plugs. I had two 1M Wireworld Platinum power cords, but rearranged my system and required longer cords. Yesterday I borrowed two Shunyata Sigma NR power cords. On the first note my wife softly said, "that sounds better". She said it was clearer. I listened for a couple hours, changing the power cords a couple of times. In my system and to my ears this is my conclusion:
The Sigma's are cleaner, definitely has more bass, a dead silent and completely black background. The Wireworld cords are more detailed, with a wider soundstage and better spacing/separation of instruments. All things considered I'll keep my Wireworld, but I'm curious to listen to other power cords.
After inserting the Sigma's I just don't understand how anyone that listened to different power cords could conclude that they can't hear a difference. There is a difference, but like any other component the individual has to decide if the change is worth it. $6K for two power cords is relatively expensive. Expensive, but oddly maybe a good value? In my system there was a definite improvement with better bass impact and articulation. Would spending $6K or just changing amplifiers yield similar results? As with most components there are trade-offs...is there a power cord out there that has the benefits of the Sigma's and Wireworld Silver Electra's? If so, at what cost?  
ricred1
So nice to read through forum posts where most posters believe in good power cords and believe in the difference they make. I have always believed that if something makes your system sound better, then there is a reason. And that reason is not a cynical "I'm being conned" rationale or a placebo affect. Like most products, when you use better stuff, better stuff happens. I myself am a fan of Transparent Audio. I once did a comparison with another audio buddy comparing comparable Transparent to Shunyata. At first listen, we thought maybe the Shunyata had the edge. There was a fun factor to it that was undeniable. Over a few days, we found that Transparent lived up to its name whereas to our ears the Shunyata had a coloration to it, albeit a pleasant one. But that coloration served some music well and others not so much. It was that revelation that demonstrated Transparent's effectiveness. And with that revelation, that first piece we listened to, when we listened again, we heard the coloration for what it was and appreciated what the Transparent DIDN'T add. But both were fantastic and both wildly better than the stock cords we replaced. Power cords are the real deal!!!
Thanks for all of the recommendations. I'm trying Shunyata again for several days. I'll post my thoughts tomorrow.
I myself am using a combination of Audioquest NRH10's, NRG100's plus one NRG1000 power cords.  I found their NRG10's to be far superior to competing Cardas as well as Shunyata power cords.  But for my Oppo 205 I find a $400 JPS digital power cord works far superior to ant current $1280 Audioquest power cord.  And that is playing my OPPO/JPS ombo thru an Audioquest Niagara 1000/NRG1000 combination.  Now the JPS power cord is only superior to even my best Audioquest power cords with my OPPO.  Using the digital JPS power cord for other purposes it sucks compared to any of my Audioquest models.  The same thing with the power cord that comes with my Rega Orisis integrated amplifier.  
I myself have been using Audioquest power cords or several years now.  Previously I used Cardas and later tried Shunyata but found Audioquest to be far superior.  Presently I am using 3 NRG10 power cords, 4 NRG100's one NRG1000 plus 2 Niagara 1000's.  I am very pleased with the results.