I sent a pm to someone regarding SEX vs Crack and thought I'd share it here. This SEX amp is good, very good. The big distinction between the SEX and Crack is that the Crack is really tailored to the 6x0. Essentially hardware EQ specific to that headphone. The crack doesn't work very well with other headphones with a few rare exceptions. If you only own that headphone, I think that the Crack can be an end game amp. But if you own lot's of headphones including dynamics and planars (yours truly) then the SEX is easily more versatile. It really took the MrSpeakers Aeon open to the next level. And that doesn't even take into account the fact that it will drive speakers. I am skeptical about the usefulness though. It almost seems like an add on or bonus feature. Until I've tested it with speakers I really can't say. But if given the choice, I would have taken some "upgrade" to the amp over speaker function, ymmv and all that. Regarding specific differences between the crack and sex. The SEX is more neutral, has gorgeous tone and offers detail in an effortless fashion. It's a great amp and I'm enjoying it very much. The crack, will always be a one trick pony of sorts for the 6x0...but it pulls off that trick in a magical way. Very addictive as the name implies. The SEX excels with 650, 800 and AFO. The signature is effortless and refined. Offering a fatigue free all day listening experience.