Trying to boost the volume of a gain channel by putting a pedal before the input doesn't usually work too well. Because the signal is already saturated to begin with, adding more gain at the input will just make it more saturated. If your amp has an effects loop, that's probably the place where you want to look at adding a boost. Whether it be in the form of a clean boost pedal or one of the EQs from the M13. That would work for both your amp's clean and dirty channels.