Power cord - 5 ft vs 10 ft ?

I put things comically, but I think gauge is important. Not all important, but important. There's a lot of information out there. My approach has been to try to spend enough so I was not using a cheap cord, but not so much that the cost started to be too high in proportion to my system.

I have heard demonstrations with power cables costing $2k and $7k and I could hear a difference -- in that system, that room. That didn't make me touch my wallet, however, because I want to change the weakest links, first, and I have a ways to go.

This video was interesting: 

I have heard 4 feet, but have never heard a difference in terms of length, so I just get a cord that gets me to the outlet on the power conditioner.

@hilde45 everything matters and the plugs make a significant difference. I have experimented with using different connectors on several power cords including stock cable and there’s definitely an improvement. 

My Dad was an EE w/ multiple patents (like my grandfather) & into hi fi from the 50"s onward. He was pretty smart & knew a lot about audio as well as electronics in general. He had a few different Dynaco power amps he built &  heavily modified to power his quite large Bozak speakers he also built from parts he got from Rudy Bozak.  I know there were two 50 watt mono amps & also a stereo 70 at one time too but don't remember if he biamped or not. The amps were on a shelf he built in the basement connected to the main floor floor joists just below the speakers in the living room w/ his preamp , turntable & tape deck in a cabinet in the living room itself. 

Anyway, he used no power cords at all for the amp but simply ran "homeruns" from the electric panel to the amps & hard wired them directly into the amps! He rarely did anything w/o a well thought reason so I'm wondering why he opted for this?

Wouldn't you think that the best power cord is no power cord? Obviously, there are practical reasons why this wouldn't always work but for folks like many here who are totally into the ultimate best sound they can get out of their systems, I surprised this is not mentioned?

Oh dear...

Another power cable length thread!

This one in any length will energize your amp with shockingly good results