Dan, interested in seeing what you come up with, but I am curious why you might not decide to do even better by just coming up with a ModWright HPA from scratch? I guess you perceive the market not being there to justify the development time and I can understand that.
Sure would be interesting though, something balanced and fully discrete with, perhaps, a tube or JFET input stage and MOSFET output stage...
I recently got a pair of Audeze EL-8 and am currently looking at HPA choices, but I'll probably end up DIYing something for my own use-I need balanced input though and there are few DIY designs out there which support balanced input (maybe I'll transformer couple)...
Anyway, I look forward to seeing what you come up with for the OPPO.