The GES is still burning-in so can't do a proper comparission right now... but I'm about 80% sure that I will be selling my HE-6 soon, based on what I'm hearing right now from my SR-507.
There was some issues with payment and bank blocked my money transfer for 30 days, so that's why I have to wait for two months... I bought used 507 on audiogon for 675, so it was pretty hot deal, so I bought them right away. This is my first electrostatic headphones and GES is my first electrostatic amp, so transformer will not helped me in any way (and I don't have any free money right now (or two months ago), it all was putted in getting GES (I even sold my LCD-2 + Silver Dragon balanced cable)), but I had HE-6 with me, so it wasn't very boring waiting of amp for 507, because HE-6 is superb headphones.
P.S. Sorry for my bad English, hope you understand what I'm trying to tell.