You might want to consider an EQ pedal. Our perception of volume has as much to do with frequency content as sound pressure, hence the "proximity effect" of cardioid microphones. What I do is use an EQ pedal in the loop (or the GEQ of my .50 Cal+ on a footswitch if I'm not using it as part of my basic tone), mostly flat except with a little bit of a bump in the low end to give it a little more thump. Basically what I'm trying to do is make it sound "closer" to the listener, the same way that a mic picks up more bass the closer it is to the source. Then I only have to add a dB or two of gain and it really cuts through on solos.