No one actually knows how to lculate what speaker cable they need

Mr.  grannyring
For the  3x0 AWG  suggestion: My suggestion was for 3 AWG at 8'.
You require 20'. That increases the cable resistance by 3 and if you go to the guage table it calls for a 3 times 0 AWG to keep it the same as a 3 AWG of 8' long.
That's Ohms law. I only use it for this suggestion.

Regaring Mr. Dill's remark of what he can hear, no one's ears can replace measurment instrumentations nor engineering calculation. Whatever you like it or not, Audio precision, HP and more are still in business.
If ears would do, we would not need them. What you can hear?
As you had tried in a blind test listening to all cables from 14 AWG to the 4x0 AWG and your ears pointed towerd a 12 AWG 99.9% pure cooper with cryo and burn in...?
Now you can hire this service, as the standard listening to IEEE.

If 10 people listened live to leaves rustling on a brisk fall day, would all 10 report the same sounds? Would they all pickup the faint sound of a wind chime in the distance? Could they all hear the same birds chirping?

I say they would all have similar, but different listening experiences based on focusing on individual things. One may focus in on a bird chirp because they are familiar with that species, another might dismiss that as noise and focus on something else. Do you see where I am going with this?

How do you measure that? Music has the same effect on the ears, people hear different things, they focus on different aspects. How do you measure that?

Measurements are only a small part of the whole system and listeners that have experimented with all that has been mentioned in this thread, like to use all the different types of cables & tweaks to create the sound they prefer. You are not going to change anyone’s minds here. Your argument has been around for decades and ad nauseam on these type of forums.

One can’t listen to cables. I listen to my system with different cables as they do or don’t sound right to me. Cables have no sound, they only contribute to the system’s over all sound, good or bad.

" Doing it with engineering skils is another. I only say that with the engineering skils, you can reach the optimum first time, every time. The listening way, of try and error could be longer, nor promising an optimum result. You may alway assume there is one better out there that would upgrade your sound, without knowing, you are already there and nothing will make it better - only worse. This is the fee of ignorance."

That is absolutely ridiculous. My ignorance is continuing to engage in this silly thread, until now ...