i got toe hear the LCD-X at the chicago meet and wanted to post some impressions for those LCD-3 owners considering the X.
i got to compare LCD-3, LCD-X, LCD-2r2, LCD-2r1 on the Master 8, the GSX MK2, and the Mjolnir/Gungnir stack. it was nice having all the audeze's there.
anyways, the LCD-X are great, but its up to you to decide. i felt the LCD-X was more like an upgrade to the LCD-2. the LCD-X definitely had the audeze warmth, it was slightly darker and more neutralish like the LCD-2, but not as dark. the treble is better on LCD-X, its not as colored. and its nothing like the LCD-3, the LCD-3 seemed just a tiny tiny bit more resolving, but its too close to call, mostly, the LCD-3 is smoother, bigger soundstage, slightly leaner in a way i think. but very similar. the LCD-3 is creamy, smooth, more colored, and lighter on the bass than the LCD-X, but more resolving (slightly), and liquidy.
the LCD-X goes more towards the LCD-2 sound. being more neutral as in more treble and less dark and closed in. theres no congestion, but the soundstage is smaller than the LCD-3. the bass, its awesome! its more than the LCD-3, its like the LCD-2 bass, but deeper and more extended. in some ways, i prefer the X and am considering it. its that magic middle i wanted, that more forward, more slam, more attack, less creamy sounding LCD-3, but i also really like how good the LCD-3 sounds, wider, more smooth, more liquid, so "yummy" as Tyll describes it.
anyways, its too close to call. i think the LCD-3 is still the flagship, but i kinda like the bass of the LCD-X more, it hits harder with that similar slam and sound of the LCD-2. the LCD-X is much more like the 2 than the 3, but they're all so similar, definitely the same house sound.
now as for the rev 1..... its more forgiving, but its also less resolving and a step below the others. it sounded great on the mjolnir/gungnir though. i know people rave about this combo, i think it suits the LCD-2 better than the LCD-3 or LCD-X but thats just imo.
anyways, if you are a LCD-3 owner. the X is great, but its too close that its not worth selling the 3 probably unless you like the slightly more LCD-2-esque presentation and are willing to trade some of the LCD3's liquidity and spaciousness for the extra bass and slightly more forward/punchy sound of the LCD-2. performance-wise, the LCD-X isn't better, the LCD-3 isn't better. i prefer both in different ways since they overlap. i like the LCD-3s overall refinement more, but i like the energy bass and neutrality (as in colorations, not neutral as in freq response) that the LCD-X carries. i am thinking of owning both, but they're too close sounding that i feel that i'd be happy with either one. and it'd be silly to own both.