How much time do you need to set-up?
Your entertainer should ideally be setup and in-place before your first guest walks through the door. Most DJ's arrive one hour prior to the start time you've given them. My experience has taught me that one hour is just not enough time to setup, test equipment, and respond to anything "unexpected". Even venues I play at consistently can have something happen that needs to be adjusted (i.e. bad power outlet, change in layout of the room, questions from caterers or other staff, etc.) My policy is to arrive at least 2-3 hours ahead of time. No event was ever ruined because the entertainment arrived early.