2 pages in and noones mentioned trip curves?
Just because you have a 20A rated breaker, doesn't mean it'll pop as soon as you hit 20.1A.
In fact, it may hold 22A for 4 hours. It may hold 25A for 1 hour and it may hold 30A for a minute. (numbers are made up for examples sake).
Look up the trip curves. Heres a modern type C MCB circuit breaker.
If you are tripping breakers, its more than likely not from a steady overload but more of an in-rush peak or short circuit (magnetic trip) condition. This is most likely from turning on multiple large amps without soft starts, or sending steady state sines to multiple channels (in-rush trip), or shorting amplifier outputs (short circuit).
Here in NZ, most modern houses use 20A circuits with 230V. You can load a circuit with 4600W, and you can load most single wall socket outlets with 2400W.
Actually, no. Well here in NZ anyway, the older the protection, the less likely it is to trip, and the more likely it is to start a fire.