As a followup to my concern about the gain level, I actually took Nick up on the offer to have mine modded for lower gain (great turnaround time, took about a week including shipping both ways). Now the low gain is -18db and high is 0db. This gives me a nice usable volume range when using the UHA-6S.MKII as a DAC with my Heir 4.As, and since I've sold my LCD-2s I don't have any cans I'll miss the high gain with.
From emails back and forth with Nick I believe he's going to soon offer it as an option you can select when you order.