Since rooms with only one circuit tend not to be very large, another circuit is usually not needed. Breakers need time to heat up and shut off, and the typical movie soundtrack explosion doesn't last long enough for this to happen. On the other hand, bass-heavy music in all-channel mode at high output levels for extended periods could end up tripping the breaker, but if that actually happens in a room like this then there are bigger things to worry about, like permanent ear damage. In any case, a licensed electrician can always be hired to fish a new line to wherever one is actually needed, a job that's easy or difficult depending on what's between the service panel and the new outlet.