The stock HD800/Gungnir v.1/BHA-1 is still the worst experience I've had in this hobby. The very definition of bad synergy. I can't imagine how much worse the MJ would have ben in that chain. Keep in mind I found a number of combinations of the HD800/Bryston or HD800/MJ that was quite pleasing with a number of various dacs. The Gagnir (v.1) was the culprit.
Wow, that's disheartening to hear. I knew the HD800 hated a lot of amps/tubes, I didn't realize it was such a diva with DAC's as well.
Not having heard the Gungnir yet, what is the issue with the pairing? Just generally unmusical/harsh?