Reading back over this thread I see some people questioning whether the LCD-2s would be a worthwhile upgrade or whether they're past the curve of diminishing returns. Or perhaps comparable results can be achieved with a different headphone/amp combination, hence the LCD-2s would be nothing special per se. These were the kinds of questions on my mind before I bought them too. In my experience many upgrades are marginal and bear no relation to price. I'm happy to say the LCD-2s are the one product that have confounded my expectations in this regard.
I unfortunately do not have much breadth of experience, however I do own a pair of Sennheiser HD-650s for comparison. I run them out of a Benchmark DAC1, both with stock cables. One thing I don't see mentioned much is that the LCD-2s completely and utterly trounce the HD-650s in terms of precision and detail retrieval. I listen mostly to rock and pop. On any reasonably complex studio recording the LCD-2s are more intelligible, they better track individual voices and instruments and vocals are easier to understand. This is not subtle. Listening on my speakers or with the Sennheisers I typically notice nice bits in recordings that stand out. It could be a sliding guitar on a Rodrigo y Gabriela album or perhaps a trumpet solo in Mussorgsky's Pictures at an Exhibition that was particularly well recorded, bathed in ambience. Such moments don't occur all that often for me. With the LCD-2s however I find that these parts don't stand out anymore, because the rest of the music has been elevated to a similar level. For me the LCD-2s do that consistently, track after track for probably more than half of my music collection. It's not merely about transient speed. It's the way the LCD-2 track small or gradual changes in dynamics and articulation that turns the music more into a performance and, for me, sustains interest far more than the relatively homogenized sound that comes out of my speakers or the Sennheisers. You can reasonably compare frequency balance and wearing comfort, I would rate the HD-650s better on both counts, but in terms of musicality and sheer technical excellence I find the Audezes in a completely different league. I have not heard the HD-800, T1, HE-6, Stax nor any other headphones that compete with the LCD-2s, but whenever I see the older Sennheiser HD-600/650 mentioned in the same paragraph, well, I cannot believe that you could ever achieve comparable results, regardless of amplification (not that anyone has asked that exact question, but there you go).
I wonder why not more LCD-2 users are drawing attention to the above. Perhaps that's just my perception. Perhaps I haven't read widely enough. Quite likely the other high-end phones play in the same league and the HD-650 comparison just doesn't come up. There are possibly some other reasons though. One is that the frequency balance is down-tilted and that the LCD-2s are quite unforced. All the information is there, and I really mean that, but nothing stands out or draws attention to itself. It's sort of musically balanced and just sounds natural to me. You have to sit down, relax and listen to a few tracks. When I do that, I'm really enjoying the above experience, however if I listen while working I might as well use the HD-650s. The LCD-2s don't especially draw attention when your mind is on something else.
The two downsides of the LCD-2 for me are wearing comfort and frequency balance. There was a substantial clamp initially (I have a big head
), however this can be fixed immediately without any protracted stretching exercises. The headband is made from spring steel and Sankar (from Audeze) encouraged me to stretch it out, saying it was easily replacable. What you do is place the headphone on your thigh, with the top-side on the thigh, then bend the headband completely the other way a couple of times (the cups will end up facing outwards). You probably couldn't do this with any other headband (not made from spring steel) and obviously you have to be careful where you grip it - you only want to stretch the headband, not the mounting posts - but I wanted to mention that this is possible and you needn't give the headband too much respect (still at your own risk, of course). With the headband fixed to my liking they are a just a little loose when tilting my head back and forth and won't stay on it bed due to the weight, but to me it's infinitely preferable to the clamp.
The other downside I find with the LCD-2s is the frequency balance. It's not completely right for me. It doesn't hit the sweet spot where most of my records sound fine or at least not the ones that I previously thought well recorded. Even with the lean Benchmark DAC1 it favors the bright recordings (my opinion). Granted, with those it is fabulous and has really made me appreciate that part of my collection, but I can fully understand people who would call these headphones dark, even congested. It's a feeling I've had too occasionally.