How to rule-out certain causes of 15 amp breaker that keeps tripping
If the amplifier was unplugged during the storm, then I would suspect that a surge damaged the breaker slightly, causing it to trip more quickly on a surge. The surge from turning lights on a few at a time isn't enough to trip it, but the larger surge caused by the amplifier power supply is.

Temporarily swap the wires in the panel between two adjacent 15A breakers. If the problem stays with the breaker, then the breaker is definitely the problem. If the problem stays on the same circuit, then the problem is NOT in the breaker; it's either in the circuit wiring or in the amplifier.



Note that the building code now requires arc-fault circuit breakers in certain areas of a residence, including bedrooms. Unfortunately, these are notorious for nuisance trips, even when not damaged. If this is an AFCB, it's even more likely that a storm surge has made it more sensitive to transients than it should be.