I use Westone ES60. It hissed with FiiO x7. Cowon and AK300 are both pitch black. I have the Ifi iematch coming this weekend. Will get you updated. It hisses with airplane mode everything turned off. It's not that bad.
It's pretty impressive what LG has achieved with the V20. The imaging is the best I have heard in a mobile device. That includes AK300, Cowon P1, Onkyo DP-X1, and FiiO X7. When you have money and experience, it's much cheaper to develop a quality dap out of a phone. Only negative for me is the hissing with sensitive IEMs, but it's tolerable.
I think v20 sounds as good as many $1k DAPs. Some make the argument that how can a phone beat a $1k dedicated DAP. The thing is that LG can sell millions of units vs a few thousand units like the AKs, FiiOs, etc. I bet the $1k+ DAPs will sell for under $500 if they can unload million + units.