I listened to the Fisher 500c just last weekend. It really does sound that good. My comments from over at Head-Fi (http://www.head-fi.org/t/741692/chi-uni-fi-8-5-chicago-area-hp-meet-nov-8th-2014-impressions):

"I’ll start with what I thought was, for me, the evening equipment highlight: Keith’s vintage restored Fisher 500C > HiFiMan HE-6. When I made it back home later in the evening, I had to Google what the large brown box was. The 500C sufficiently tamed the HE-6’s treble peaks/etch while allowing the clean high range to come through. The 500C added smidge of warmth to the HE-6 but it didn’t remove any of the HE-6’s attack or crispness…nor did it introduce any smear or stuffiness. Talk about slam: the 500C let the HE-6 dip low and deep – and then hit you in the face with its impact. When I got up from listening to “Billy Jean” I think I was still feeling the bounce. Great combination, an engaging and enjoyable listen!"

I'd definitely second that nomination, to be added to the Vintage/Out-of-Production pile.