Are there better options than a TPA3118 60W Mono Amplifier Board (???) -- it would need a DC-DC boost converter to get supply from 5v to 20v. I assume there is an efficiency loss there. Looking for a more elegant solution...
Use a laptop battery, or 18650 cells in series.
More voltage, and more options.
Discharge rate at 60 watts will maybe cause a fire in power bank, which is dangerous, as you are asking 12 Amps from a 3.7V cell boosted to 5V.
That is Englishman speak, an American would use stronger language.