What was the first power cable that you noticed a difference in the sound?

Shunyata NR power cords. Alpha on amp. Delta on Line stage. Venom 10 on SACD player and phono amp. They really do reduce noise so you can hear deeper, wider and taller. 

Run Jim run as fast as you can. Just drop the cords and run. This goes on forever and ever and ever. That’s what they want you to do. It never ends, unfortunately it looks like you got taken for a ride. Don’t feel bad it’s happened to all of us at least once

Have to say that it wasn’t even an expensive cable that made a notable difference in my system. The first one wasn’t exactly an improvement, which was a Pangea MkII. But it still wasn’t one very much more expensive after that one that made a serous improvement, either.

For me, just a well made aftermarket cord with decently fat gauge, quality shielding and that is well terminated. But to that, nothing made as big a difference after some better “cheap” cords than introducing a Chang Lightspeed power bar. Better yet, separating digital front end with a separate power bar from the one used for the preamp and power amp.

Still waiting. See I'm one of those guys who actually took a physics class, studied power distribution and networking, and practiced it professionally for nearly 50 years, and have seen and heard, if not all, most of the tweaks in that time.

Here's one - the original Monster Cable demo had 18 Ga lamp wire rolled in a coil behind the switch while the Monster Cable was laid straight. No surprise the Monster Cable A/B'd better - the coiled lamp cord was a series inductor, AKA a low-pass filter with measurable DC resistance. Trim that out and the difference went to zero. 

If a power cable 'lowers the noise floor', that would be measurable, and might just help things.  Anybody ever measure that? Yeah, didn't think so. 

In my system, QSA Lanedri, and I've had the Argento Flowmaster Reference in my system.