You'll definitely find yourself using different settings with a different amp in the mix.

Before you add 6dB to everything, I'd like to ask why you want to change the center to +3 instead of -3. The calibration should yield the same volume because you've calibrated to the same reference level in both cases. If you find yourself wanting to turn it up five or six dB higher than you used to, you absolutely could bump all your levels up by a few dB.