Ive heard the general rule of twice the watts to make a 3 decibel increase. But then how many decibels does a 10w amp put out at say 5 feet? How about a 100w? Or a 500w at 5, 10, or 20 feet? If I had a 3,000w PA system running, would an increase to 6,000w still only add 3 decibels?