!) I got fatigue from the Bryston BHA1. I sold it and got the Benchmark HPA4. I used the Meze Empy with both. This is a warm and relaxing headphone. The hardness on the BHA1 that gave me fatigue was not there with the HPA4. Though the HPA4 is not warm at all so a bright or neutral headphone may not work for someone that likes some warmth..
3) I went through a few DACs in the last 18 months. The very best one by far is the Musetec 005. There are 2 threads on A’gon talking and arguing about it. This is an end game DAC for me. You may like the Gustard X26 Pro which is half the price and warmer. I sold that to get the 005.
I recommend the RAAL SR1a to everyone but for you that will not work since other people will hear the sound. More so than regular open headphones.
A’gon is not really headphone central. Check out Head-fi.org and my fav reviewer soundnews.net for deep dives into headphones..
I should add that I sold the HPA4 and Meze because the RAAL SR1a was so much better, and this headphone needs a special amp or regular 2 channel amps/