I find myself doing a lot of mixing of designs, mostly using different kinds of transistors within each circuit.
I have found 2 mods to Joe's designs that really made the sound for me:
For the vulcan, put a BJT in the middle stage, with the gain slightly decreased in the first stage and increased quite a bit in the second... Kinda like a hybrid of the JFET and the BJT design...
And the Blackfire, put a TransFET booster in the place of the second stage. I haven't had the opportunity to experiment with MOSFETs yet, but I think it could sound pretty damn good in the output stage of a blackfire.