Mains Power Cable DIY

I'd like to DIY a main power supply to my system.
I'd like to do this in two or three stages
1st to build a power cable from the wall to my amp
2nd to build a mians distribution for all the gear

And 3rd: I'm waiting to renovate my condo.
At that time I'll have a primary circuit from the panel to stereo run
If anyone can offer their experience and specific details I'd much appreciate it
Currently I'm running an old "gang box" ....something I made during my construction days. Tonight I took the wall socket apart , cut it back and reconnected everything and there was a fair difference in what I heard.
I'm specifically looking at wire sizes and recommendations for shielding and what it all looks like. TIA. Appreciate your experiences