Practically speaking, a breaker is going to be just fine-springing for one that is marked SWD wouldn't hurt-but many breakers are used to switch light loads at or near 80% of their capacity. Powered speakers will normally power on under a very light to no load condition.
In our install, we are using a light switch and it is working just fine. If you have a secure location for a switch that is not a bad option. A breaker is less likely to be inadvertently switched off. IMO, the choice would depend more on the practical considerations-convenient to use, but obvious as to its purpose and controlled.
