Are manufacturer AC cables good enough?

You sure ask a lot of questions. What are you, a narc? Independent verification requires someone uh, independent. That’s why they call it independent verification and validation. Are you volunteering again?

"Synergistic Research also claims to do exhaustive double blind testing, but again, never publishes anything, nor allows independent verification."         Excuse me? Synergistic offers a 30 day satisfaction guarantee, on virtually everything it sells.       That should be sufficient time, for even the most obtuse, to discern whether a component change results in an audible difference, in their own system.      Ever been to an electronics trade show?    Mr Denney goes to lots of them, around the globe, at which he demos his wares, openly, proudly and with great success.     ie: https://www.synergisticresearch.com/best-of-show-awards-2015-all-major-shows/

Mr. Denny has never done a double blind test publicly. Never. He refuses .. or makes excuses. Take your pick. But has never done double blind with any verification or validation. 

turnbowm, heaudio,
Please list the aftermarket power cords you have compared to stock power cords?