Everyone seems to be so surprised over the dr.z amps, they're fine to be sure, but nothing out of the ordinary, he uses the EF86 to amplify the signal big time in the first gain stage (which some brands have experimented with in the past, like vox for example)... After that for the 28 and the route 66 it's nothing but brown era stacks, long tail phase inverters and power stages with out negative feedback... all pretty standard stuff, even the components he uses are mostly shelf stuff, not great stuff like brands such as Clark...
even the fact that the controls are interactive and add gain when dimed is not out ordinary for anyone familiar with a tweed or brown fender.
I much rather look at amp makers like emery sound, clark, allen or even mission amps, even though I like the dr z amps there is nothing extremly original about them...