When you say a room with about 100 people in it, does that mean a crowded 100 people? or 100 people with space to move around? And how loud do you want your system to be with those people in the room? Do you want it ear-splitting loud or do you want people to be able to talk to each other while the music is playing? Of course there is also speaker placement. But I'm sure that you have already asked those questions of yourself. First impulse is to buy or build something massive, but if you are planning on just "small" clubs and private parties, maybe you should think a little smaller. After a few years of loading and unloading my system out of a trailer, we have started to use a bare-bones system, both for ease of loading and quickness of setting up, and playing. I play in a three piece band that plays a lot of classic rock and blues. We try to keep equipment up to date and be as professional as possible. Hopefully, I made a few of your questions a little easier to answer.