I have the 250ohm and have been using a combo of dacs/amps. Until my 789 arrives, I’ve been mixing and matching my monolith thx portable, Massdrop CTH + SDAC, SMSL D1 + ZDT Jr, and I just got my Airist R2R and Dark Voice, so I will be trying that combo soon. Aside from the THX portable, everything has been a tube or hybrid, so maybe that’s the issue but I just feel like I remember the 770s sounding better when I heard them in the past. I can’t find it, but I want to say that Metal571 had mentioned a change to the sound signature of the 770s in one of his recent videos.
More than likely the issue is that I just have purchased and demoed much better headphones since I initially tried the 770s. When I first heard them they were as good as or better than anything I had tried previously, so I always had them in the back of my head as something to buy down the road. By the time I did, I already owned better.