I've been using them with Sennheiser HD 800's for about two years, and have been very happy with them. Very natural sound. I would absolutely buy them again, with the proviso that I'd like to hear the Pass Labs headphone amp before committing. I'm a fan of Pass Labs from hearing their stuff, but haven't owned anything from them.

Good luck with your decision

Living room: 818v3, Audio Research D150, Maggie 1.6
A/V room: 861v8, DSP7200SE L/R/C, 4x DSP320 surrounds, ID41 + Roon, UHD722, Prime+PS