Are manufacturer AC cables good enough?

No doubt there are many of you who have decided that throwing money at a power cord is a necessity. I almost did the same...almost. I was later told (by someone in Binghamton) that McIntosh power cables are specifically designed/included with their gear and that there is no need for aftermarket. I was advised to use the money for more music or other components. I took the advice.No Kool Aid here.

I wonder how many of the nay sayers who claim power cables do not make a difference have even tried upgraded PC's?  To me, they either have not tried or can not hear.  And it is usually them who cite science to explain away any possible benefit.  I certainly did not want to hear the difference I did, it would have saved me money.  I did try and I did hear...and not subtly.  I have dedicated 20 amp lines, and upgraded outlets.  I still heard better music with better cables.  Maybe audio manufacturers should take the approach of auto companies.  They could sell a DX model, a GX, and a GXL.  The base model would have cheap cords, cheap feet, less expensive connectors and a dull faceplate.  The GXL would come with vibration absorbing feet, better connectors, a nicer faceplate and a metal vs plastic remote.  Then everyone could be happy!  Certainly folks who drive eco model cars think they are just as good as the nicer version, and don't appreciate the grippy tires, added horsepower, bigger brakes and navigation!

I went to such a test.  About 50% picked the more expemsiver power cord.  We did find a difference in interconnects, but only the very cheapest were picked very often as the worse of a choice.  The others were about 50-50, with mostly guessing.  There was never a consensus, except for the decades old, cheapest crap from Radio Shack.  Basically, any cord with oxygen free copper was deemed somewhat better, but that could simply mean they were put together better, or had better insulation, etc.  One exception:  If your power cord runs parallel to your interconnects, or even crosses them, better insulation/grounding might help. 

How good are the power wires running behind the walls to your power sockets?
I don't think it would make sense to buy expensive power cables if the wires supplying power to your sockets are of regular quality.

I did try and I did hear...and not subtly.

If you did not try in a blind controlled test then you're just offering subjective biased opinion.We ALL have subjective biased opinions when it comes to seeing and hearing the only way to know if something actually works is to remove the biases as much as possible. One of the best examples of conducting an ABX test is done by Floyd Toole when he was at Harman. It's controlled by computer and the results from blind compared to sighted is very revealing. It's and hour long if you care to watch it. 
https://youtu.be/zrpUDuUtxPM