heliosphann
Headphoneus Supremus
The Audeze Sine comes to mind. For a serious attempt at inexpensive, resolving planar headphones the result was surprisingly good when I tried them.
I just recently picked up a pair with the over ear VesperAudio pads. Was impressed with their sound quality and with those pads they're comfortable with great isolation. However, I found them to be shockingly hard to drive for being portable headphones. I couldn't even power them adequately out of my old DX50 and I was in the high 80's - low 90's out of my Cayin i5. For reference when I was using my old Ether C's out of the i5, I was only at mid 70's.
Just seems like a very puzzling decision by Audeze to not make them easier to drive.