Are manufacturer AC cables good enough?

I recently substituted the stock power cord I got with my Mytek BB with a Shunyata Diamondback I fished out of the closet.  I won't tell you how it got there because I'm not really sure.  Short story shorter...  Dad gum, it actually made my stereo sound better.  Practically every single audiophile parameter, from soundstaging to understand-ability of lyrics to orchestral string tone, got a five to ten percent boost.  This happened with every source, as I use the Mytek as my phono amp in addition to using its streamer/DAC functions.  Huh?  Wha?

I take sound quality extremely seriously, but I'm not inclined toward drawing my sword whenever I come across an opinion I don't agree with.  I actually enjoy all the backbiting endemic to this site.  It's okay.  Blast away.  As long as you guys don't start dropping multi-ton mono amps on each other's toes.

Stop worrying about crunching data.  Stop worrying about whether you've been peddled snake oil.  It's okay to go goo-goo-eyed over a price but if the price is comfortable to you after you calm down a little, why the heck not?  Over the years I've decided that purchasing hifi is as subjective as purchasing a musical instrument.  Expensive usually means better but that doesn't mean you can't enjoy the heck out of a less stratospherically priced example of the breed.