Jason, the actual formula for the dB relationship between two power levels is 10 log(P2/P1). For example, the log of 2 is about 0.3, so when power is doubled this results in 3dB more loudness. This is true regardless of whether the increase is from 1 watt to 2 watts, 10 watts to 20 watts, 100 watts to 200 watts, etc.

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Enjoy the music, not the equipment.