Excellent review. Thanks.
I do agree with everything you said.
About the quibbles, I do have a not so small one to add. While the GS-X Mk2 sailed through nearly all of my HPs, namely the HD800s, TH900, Utopia, HE1000V2 and even the venerable Grado PS1000, it did run out of steam with the ridiculously inefficient HE-6. But that may not be such a big deal now since the HE-6 has been more than ably replaced by the HE1000v2.
Regarding the DAC, I found out that it is really not the fault of the Sabre chips, but rather the inadequate design of the analog section. My stock Oppo 93, 95 and 105 all mercilessly tortured me with their ear-piercing highs and unbearable sibilance. Even the new Oppo 205 with its much improved audio section is not entirely free of these problems, problems that the GS-X Mk2 reveals mercilessly. In come the Mod Squad. I had my 95 modified to the ModWright version with a separate power supply box, all tube analog section and Audio Magic wiring. The difference must be heard to be believed. The high level of transparency and detail remains but the unbearable highs are replaced by the most glorious, sweet, delicate sound I ever heard. Even the sound stage and depth improved immeasurably.
Unfortunately, all theses significant improvements came at a cost. Nevertheless, I am having my Oppo 205 mod-right. Is the additional $2900 worth it?—currently $2000 for the early birds—I don’t know. But people spending $3,000 for a pair of headphones has long abdicated their right to complain about prices.