In my trails I could not find a magnet planner Headphone I truly loved, some came close but none totally clicked. I did not really find online reviews any help. 
My time at Audio Sanctuary convinced me Electrostatic headphones where the way to go, but decent ones are not cheap.
I did a lot of research and as always it is easy to get lost in all the different opinions and preferences. 
In my research I came across Mjolnir Audio. He makes Engergisers and also sells used equipment.
In my experience dealing with Birgir is like entering a different world. I mean this in a good way. Here is a snippet from his website to give you a overview of the man.

"I’ve been building electrostatic headphone amplifiers for close to two decades now and I used to sell off the ones I had no use for. My partnership with Kevin Gilmore has been very productive so we’ve been active in coming up with new amp designs over the years. This means a lot of amps have been produced which are now in use all over the world. One rule has been in place since day one, I will only charge what something costs to make and not a single cent over that. Same goes for all the DIY parts I’ve had custom made for my use over the years, I’ve shared them with enthusiasts all over the world at cost. Profit, or at least the hope of it, kills the community spirit inherent in the DIY world which is why we give away our designs and free time to help others".



To be honest I have no idea how he does this. I tend to imagine an eccentric millionaire based in Iceland 

I decided to go for one of his used Stax 007 mk1. He prefers this to the SR X9000 which is saying something and only places the mighty Omegas above them. I just do not have the knowledge to comment on this, but due to his Ethos I am willing to trust.

Here are a few reviews of the amplifier, as quite a rare beast.





audiophilestyle.com/ca/reviews/electrostatic-headphone-amplifiers-review-mj%C3%B6lnir-audio-carbon-cc-and-headamp-blue-hawaii-special-edition-r1180/