I've played four Dumbles. Each was unique, and two sounded like shit IMO.
Howard/Alex built his amps to the customer's requirements, so each has it's own voice. When you go to copy one, of course the question is, is it one of the good ones?
A cheaper and easier way is to get a Bruno Super 100 clone. Tony took apart the four Dumbles Gene of Ultrasound owned. He tested every single part in each amplifier and documented the results. Tony builds the clones as exact copies of the originals. I've had three of these clones and they were fantastic and better than the two shitty real Dumbles.
You don't buy a real Dumble without playing it first IMO. If you can't afford to fly to the amp to try it, then you shouldn't be a customer.
The moral is always the same, not all Dumbles, 1954 Strats or 1959 Les Pauls are heavenly. Some are, most are average for their time period, some suck from the get go and other aged poorly. Don't let the hype consume you.