Not directly related to tube amps, but I’ve had very good results running my vibrandoneon –using the internal Sennheiser mic system Victoria installed for me — through an Acoustic Image Corus +. Super transparent sound.
With regard to getting distorted sounds, I’ve been playing around a bit with Crumar/GSI’s Burn pedal. It’s a great Leslie sim with built in tube distortion and other effects. The problem I run into is that the acoustic sound of the instrument is right in front of me, making it hard to hear the effect live, unless I really crank the volume, which I don’t like doing. At any rate, I’ve gotten some nice crunch and color from that pedal.