I believe that photo is from the October Los Angeles meet, right? Craig had that there as a prototype he had made - and unfortunately didn't have the power supply so we didn't get to hear it. If I remember, I think Craig planned to keep it for personal use.
Wonder what tube setting were chosen by those who ordered a Balancing Act ?
My understanding of available options to be decided at time of ordering :
I go for the 300Bs simply for the wider choice of old and current production tubes available. AD1 was only made by Emission Labs today, and 307A are not that common, and great NOS ones seems to be quite difficult to find these days ?
If I had the cash I'd have a BA as to me it represents the best headphone amp I have heard (and I have heard most of them). I'd most likely go 307a if I were flying blind as there are still 307a stock out there if you scrounge. The AD1 should be a great combo but I have not heard it to say. The AD1 is either new from one source or used telefunkens for big bucks. The early version of the BA that I had at my house was great and that was before Craig did a full throttle power supply.
If you order either the 307a or AD1 buy 2-3 extra sets of tubes and that should set you up for the foreseeable future.