EISENbricher
Headphoneus Supremus
I found that different headphones react differently on NX1. With my old Beyers, the bass becomes drier and overdamped, making them sound brighter. With Senns, any of them, it is quite opposite, I have a feeling of increased bass, and more control.
On another note, since you are mentioning so many sources, would be very interested to hear how do you rank all your daps in terms of soundstage.
As per my findings NX1 is slightly cold sounding amp.
In short it may make analytical /flat sounding phones to sound drier but it does a very good job of taming bassy earphones.
I haven't had experience with headphones but for most of my IEMs this holds true.