PA Speakers for Parties

Hello,
I am brand new to this whole scene. I am in a fraternity and got elected to run certain aspects of our parties. What we need are PA speakers (our old ones broke) They need to be self powered, I am not really sure what exactly a decent setup would be but parties are generally in a huge room with close to 100+ people. We had two older speakers that managed for a few years before biting the bullet. Anyone have any leads they can give me or tips, brand new to this whole thing.