Hey man, this is your amp tech Scott, we briefly talked about this last night when you dropped off the Mig, but I really feel that maybe you should try out a Sceptre or one of the other 2xKT88 variants of a Sunn head. Since your Solarus was a 40 watt version.
Especially with solid state rectification. They put out a good 80 watts and you will absolutely get more volume.
So, look for 2xKT88 heads. These come in a large variety of names. Sceptre, Solarus, 190B, 190L, 200s, 100s, Sentura 2, Sentura 1, Sonic 2, Sonic I-40, Sorado, Spectrum 2.
They are all basically the same amp, just some have reverb and tremolo, some are tube rectified, some are SS rectified.
The tube rectified versions can put out more power if you put a plug in SS rectifier in them, this will increase the voltage by 20% or so. You will of course have to rebias the amp for this higher voltage and make sure the caps can handle it.
Isaac is correct that putting a master volume would only be useful for getting more distortion at a lower volume.