I'm really enjoying my BHSE / SR-009 / K-01 combo, but until I receive the GS-X, quite a lot I'm using my Pico Slim / HD600 with that source and the SQ while not as good as the BHSE / SR-009, it's still very good. Be interesting what the sound will be like when using the GS-X, as opposed to the Pico Slim.
I've also got a 4 pin XLR silver custom cable for my HD600's to use with the GS-X.