Do I need upgraded power cables?

I have been listening to audiophile grade equipment for 25 years. The first items I bought came with an upgraded, aftermarket power cord (for amplifiers).  Since then I have used mostly standard power cords with my other equipment.  Over the years I did try one or two slightly upgraded power cords ($50-300) in my pre-amplifier and other components, but didn’t hear any difference.  Last year, I bought standard power cords for my amplifiers, and didn’t realize it initially, but it did slightly affect the sound quality in a negative way.  Just this past month I demo’d markedly expensive power cords ($1,500+) in my pre-amplifier, and heard a rather significant difference:  it affected the timbre of the instruments, and slightly enhanced the clarity.  This was a difference, but was it better?  Some parts were better, but overall it was just different, kind of like trying different interconnects.  Prior to this experience, I did not think a power cord could make much of a difference.  While I was experiencing this, I also learned a bit of electrical engineering, about how AC waves can have reflections at interfaces, due to different impedances of the conducting materials, which can create an interference pattern in the otherwise 60Hz wave.  Maybe that is part of what’s happening, maybe it’s something else.

@westcoastaudiophile 

I bought some new, but inexpensive standard power cables for my amplifiers to see if they sounded better than my old, but more expensive power cables.  The new cheaper ones that I bought were just new extension cords with 12awg OFC copper wire, with just a black rubber covering.  The contacts were tight for all cords.  They didn’t make it sound much worse, but it was flatter, slightly more muffled sounding.  However, a much more significant difference was comparing the standard power cable with an expensive one plugged into the pre-amplifier:  very obvious, marked difference.  As mentioned, prior to this experience, I had tried upgraded $100-300 power cables in various components, but didn’t hear any difference, so I did not think power cables really made a difference.