I continue to believe that the HD600's sound great on the Crack. HD600's sound pretty much the same on the SEX.
The T1's sound ok with the Crack and much better on the SEX. T1's are higher resolution cans and it seems to me that the SEX is a higher resolution amp than us the Crack.
The HE560's are a bad match for the Crack and sound excellent on the SEX
The Bryston BHA-1 is also a great amp, but a different flavor than the Bottlehead gear. All the headphones sound at least very good through the Bryston
Overall, I think the most musically satisfying amp is the SEX. The Bryston is the cleanest amp and likely the most accurate. It's also the most flexible
Crack/Speedball, SEX 2.1/C4S, Bryston BHA-1
Sennheiser HD600/Cardas cable, Beyerdynamic T1 2nd Gen, Hifimam HE560/Hifiman balanced cable