I’m not sure if a 20A cable will sound different just because it is a 20A cable, but the P20 will provide more power and probably sound a little better when fed with a 20A cable from a 20A circuit. If you only have a 15A circuit no point in the 20A cable. Having said that, I would strongly recommend running a 20A dedicated line with 10 Gage wire for the P20. That will give the best performance out of the P20.
