@hillbilly559 Thanks for all the info, especially about JM Audio. I was not familiar with them. Reasonable prices for what looks like great products and service.
@yyzsantabarbara I bought the Gan1 and had it modded partly on the basis of what you posted on Agon. I have not been disappointed. Thanks for that. The Raals look fantastic but are more than I want to spend, at least for now. I am setting my headphone budget at $2k for now. I think that will get me a significant upgrade from the HD650s. I'm afraid if I spend more I simply won't appreciate it. My ears need some training.
To support whatever new cans I get, I'm leaning toward a tube amp, say from Woo or Feliks. Upscale has a couple of Feliks Echo MKII amps for under $1k. I'd pair that with an appropriate streamer/dac. Perhaps the Fiio S15. In any event I think of my goal now to assemble an entry-level high end headphone system costing maybe $4-5k and then see where that takes me.

