I believe if you purchased a Dumble you could arrange for it to be modded to suit your sound more, though generally Dumble himself did not like second hand sales of his amps, as they were all tuned to the player. His business model was indeed quite different, and as time went on he had more and more custom stuff like the HRM mod and other things. Just looking at the Ceriatone website shows 10 different "styles" of Dumble clones. Both Amplified Nation and Two Rock also have a good number of models, while Fuchs seems to have kept it a bit more streamlined.
Still there are supposed to be some specific things that Dumble amps are known for, like the transparency, and the "bloom" of the overdrive.