Most of the posts are listing to use heavy gage wires.
The wires from your circuit breaker to your outlet are most likely Romex 14-2.
These are solid copper.
We use stranded power cords because they are flexible, not because they are better.
Your amplifier will only momentarily require high power at real high sound passages. You most likely have 100,000Mf of storage inside of your amplifier to handle these.