It all depends on how loud you want to listen, how much bass you expect and what kind of music you play. No simple answer.
How large of a speaker do I need
I am moving into a new place and my new listening room will serve double duty as my living room. It is about 15x15 with an open floor plan-one end of the room open to the rest of the house. Do I need to be concerned about low frequency "bass" leaving the room (ie: lack of reinforcement due to 1 of the walls missing and no ability to shut the door). Thanks for your input.