Further to Herman above, each doubling of SOUND PRESSURE level (i.e. spl), i.e. what we "listen to", is 6dB. You need four times the "power" to achieve double sound pressure -- in fact twice "as loud". Yr mic should record +6 dB when your power rises 4times.
In other words... on paper, going from 200W to 300W gives you an extra 1,4dB. That's assuming, of course, that the speakers can take 300W continuous -- which they usually can't.
In other words... on paper, going from 200W to 300W gives you an extra 1,4dB. That's assuming, of course, that the speakers can take 300W continuous -- which they usually can't.