FYI to all considering the 789, here's a highly favorable review of the device:
https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-massdrop-thx-aaa-789-amp.5001/
As for me...I'd love to get this, but I'm still happily enjoying my Topping A30, paired with the matching Topping D30; the cans I'm using are the HiFiMAN HE4xx. I got all of the mentioned gear from Massdrop in the past year. The A30 and D30 were also reviewed by amirm of Audio Science Review, and while the A30 doesn't test as well as the 789, it's also more than twice as inexpensive :-( Still, I'm enticed by what amirm said about the 789: "...Buy one and be happy forever." hmmmm...Santa baby... ;-)