The only problem with mixing yourself on stage is that you can't hear what it sounds like to the audience, and someone has to keep walking out into the house to get a level...then you can never get a mix right because you can't listen to yourself...unless you have a long cord.:) (Which a lot of people do....keep the bawdry to yourselves.) ;) Otherwise, if you have someone in the house who's ear you trust they can always tell you up or down...although that's only half the battle. :) All in all, if you don't have a sound person that you trust, get one. That way, even if you have to deal with one you are given, most engineers (I say most) are ok with having another engineer tell them how this band is supposed to sound, especially if they're not familiar with the music.