I had the LCD-XC for a few days as part of the HeadAmp loaner program. I did some comparisons between the LCD-XC and my LCD2. Music was mostly classical but some rock as well in lossless and high-quality MP3 format. Source and amp were HeadRoom Balanced Max as well as my Merdian G08 plus Eddie Current Balancing Act. Headphones were listened to in balanced.
Pros. Compared to the LCD2, the LCD-XC offers more of pretty much everything. Instruments and voices are more full bodied, have greater weight. Separation and detail retrieval are better. Notes and voices are more nuanced and pronunciated. The bass while not deeper is stronger. The highs and sound stage are on par with the LCD2. The headphone is easier to drive than the LCD2. At the same volume, the XC is louder (or appears so). I find the XC to be very comfortable. On the whole, the music has more presence.
Cons. This greater presence is partly due to the presentation of the LCD-XC being more forward. This is not always a positive. There is a fine line between music having presence and the sound being aggressive. In addition, and probably related, the treble energy is strong. Some passages or recordings are irritating to listen to (bright). The LCD-XC is very different from the LCD2. Although better in most areas, it lacks the smooth, laid-back sound of the LCD2 that I have grown accustomed to.
In Sum. The LCD-XC is a wonderful looking and very solid sounding headphone. I often found myself entranced by the music. There are moments where, in these closed headphones, it is just you and the music to the exclusion of the outside. The price is a bit of a turn off although (I suppose) in line with other high-end headphones. On the other hand, I could see myself listening to these daily and deriving much enjoyment.