shboom brings up a good point about making sure the overall sound is balanced for the audience. That can be hard to do from the stage. I have a wireless system, and I'm kind-of the default sound-guy for our band, so I wander out into the audience during sound checks (which sometimes is just our first song due to time pressure) and listen to the overall balance - and out there I can also stop playing my guitar for a bar or two (ostensibly for dramatic effect), then jump back in, to see where I'm sitting in the mix. Anyway, I think it just takes a bit of patience. And I think the best advice so far has been for everyone to turn it down...way down...and then tweak from there, slowly upping everyone's volume until you are comfortable (and no further). If everyone is already nearing max, the wall of noise is hard to tweak.