hosting a live band event? very good!
First, you should have all the equipment you need. A more advance mixer and amplifiers (both house and monitor) are important, speaker system just ensure the rating is right will do. make sure you have enough monitoring speakers.
If you are not so sure, and also don't have the equipment. My advise to you is to engage music company to do it for you. They will know want to do, and what you need.