The old theory was to play loud on stage and then the sound guy can take care of everyone else. More gear to hear yourself the better.
At one time I subscribed to this theory.
Since then I have learned that it is not about the stage volume. It is the total mix of the FOH, Monitors, and the Stage volume.
I haven't played, lately, in a large venue. But, I would think that if you were using an 8x10 on one side of the stage and another on the other side that should be plenty for the stage volume - your amp sound. Then the Direct out on your amp/pre amp should feed the house and the monitors.
I agree with many of the other posts. Learn to play within the limits. A better, not necessarily better, PA is in order.
Go to the big shows and look at what they are using. Take that information from every live gig that you see/hear and make the correlation. What should you be using for a particular room. In my mind it takes at least 2x the bass to the mid-top end of the pa to work a room correctly.
I am playing rooms up to 600+ and my 410 fills the stage nicely. I use the Direct/Recording out and feed the FOH and the monitors. The guys in the band do the same. They sound guys love the setup because they have complete control of the room. They can add, subtract, and many other math things, to make the sound amazing for the audience - as it should be.
Let go. Let the FOH do it's job. Make the monitors do their job. And have the correct concept with your onstage sound levels.
Not a slam, please don't read that into this post. Just info from an old guy.
