There is another reason to look more closely at the 813: it is easier to drive than the 845.

Also, no sense going to all the trouble of building when the parts or design are not top-shelf. THe assembly/craftsman labour is the same either way, might as well build a really good amp.

Another thing to lean toward the big ones: I already have a medium sized one, a 3-6 dB increase is required to be worthwhile. The medium sized amp is going to gome in at about half the price of the big DH amps with proportionally bigger power Iron.

If it were easy, everybody would be doing it.
regards,
Douglas