I agree that trance is not all about bass. I will go further than that - I think trance, at least the good stuff, is one of the hardest genres to get right (here I'm talking about stuff like Hallucinogen, Jaia, Spectral, old-school Infected Mushroom and Astral Projetion, etc.).
Really complex albums are pretty much the musical equivalent of a sine sweep - they engage all frequency ranges simultaneously and have a lot of layers one on top of the other. Here you need tonal balance, to make sure that nothing is given undue emphasis; speed, to make sure that no single layer interferes with the clarity and resolution of another layer; impact, to make sure that the tactile component of the bass is present at least to some degree; flat/linear highs, to make sure that the treble isn't harsh or sibilant and doesn't do anything to distract from the rest of the presentation, and you also need good imaging to make sure that the spatial cues and reverb, when they're there, are properly represented. Midrange tone isn't quite as important here since instruments are usually very heavily processed, but on some disks with well-recorded acoustic components bad midrange tone will make itself painfully known too, and I definitely prefer headphones with natural mids for trance (and for everything else for that matter).
Not a whole lot of headphones do all of the above. In fact most don't. A well-driven O2 is one of the few that do (whereas a poorly-driven one really can't hack it). The SR-003 is nice too if you get a good seal, and so, strangely enough, is the UM3x. Or maybe there isn't anything strange about it since balanced armatures combine speed and impact, while the UM3x's tonal balance takes care of the rest. Can't wait to hear the JH13, something tells me it should be wonderful with trance.