I've been using the LCD-2 rev2 with a Lyr (Lorenz tubes) and bifrost (recent) for about a year as my only real headphones. I've owned the HD800's in the past and really enjoyed them for the level of detail, soundstage, and space. I've kept the LCD-2 so long because they have great emotion, female vocals are fantastic, and the low end is very enjoyable.
I'm ready for something new and have been out of the headfi loop for a bit. I see Denon has some new monstrosity coming out, an interesting release from Fostex, LCD-3, and even a HD800 isn't off my radar. I'm really looking for something that would be in between the HD800 and the LCD-2. Something that had the level of detail, space and staging of the HD800 but more low end impact and a bit more emotion, especially with vocals. A friend recommended the hifiMan 500 but I would love to here some additional feedback. I'm not really interested in changing out the amp and dac right now but if I find a headphone I really like I would not be opposed to building around it.