The LL1630 is a nice transformer for the job for something off the shelf. I do wonder why anybody would use the LL9202 let alone the AM version. Wholly unsuitable for this role.
There is not only the Demograf on electrostatic market. I've heard two other very interesting things – Dubiel Accoustic Euridice and LRT.
Euridice is complete tube amplifier, generally better for SR-007 than any Stax amplifier besides SRM-T2;
LRT is very sophisticated version of old Stax "adapter for earspeakers" with which and my ASL Twin-Head preamplifier paired with Restek Extent dual mono amplifier Stax SR-009 sounded better than with Orpheus or T2.
This better than the T2? You do know its the same crappy circuit as the King Sound M-20 but with even worse tubes? Just about the cheapest way to drive Stax that is possible.