I think what Rx8man is saying is that the same power cord used on 2 different components may not yield the same improvement from component A to component B. Nowhere in his statement did he say that there is no improvement. My experience mirrors Rx8man's. Trust me, it is not because I am not using or trying aftermarket power cables. IME some components are not affected as much as others by upgrading the power cables, though the sound is improved. I also think your statements are far more alike than different. YMMV.
Power Cords - Just Say Yes
I'm the biggest cable skeptic on the planet. I've never been able to tell the difference between one speaker cable over the other. I've never a/b tested because I just can't handle that sort of thing when all I want to do is listen to music. The power cord however is a whole different beast. I know. I just replaced a 18/3 that was powering my Rogue Cronus Magnum for two years with an Audioquest NRG4. I know some people aren't fans of AQ but that's what my local guy sells and I support him 100%. He sold me a broken in demo which is exactly what I wanted. I didn't do an a/b test and I didn't have to. I pulled the old one out and tossed it in the copper recycling pile and replaced it with the AQ. I fired up my amp this morning and let her warm up. I pulled out Sylvain Luc & Bireli Agrene's 'Duet' and hit the play button on the remote. Right off the bat I had to blink my eyes to make sure I was actually in my house. Everything tightened up with a dead silent background. I feel like a fool for waiting so long to come around on this one. I'm still skeptical of whether or not I will notice a difference when I replace the power cord to my CDP, but if you tell me I'll notice I might believe you. Either way, that's my next investment.