I am no longer exclusive with my Crack. I've just completed my SEX amp- bone stock, no CS4 (yet, but I have the parts)
Still using high impedance headphones.
Yes, the Crack is stupendous, and the SEX is superb! Dare I say cleaner?
Crack/Speedball, SEX 2.1/C4S, Bryston BHA-1
Sennheiser HD600/Cardas cable, Beyerdynamic T1 2nd Gen, Hifimam HE560/Hifiman balanced cable