Since I will probably never get around to posting anything formally on spending 3 weeks with the HD800s, HE-500s and LCD-2s, I figure I'll post some quick impressions now. In few words, I found the HD800s fantastic, and more than able to keep up technically with my LCD-2s. What surprised me was the bass response on this phone. After all I'd heard about it over the past two years, I'd never have expected that. Even several encounters with it at meets with good systems did not "reveal" this part of the HD800's abilities.
The bass was extremely fast, resolving, flat and deep. It even seemed to be neck-in-neck with the LCD-2 in surface bass detail. The midrange was clean and accurate, but the highs had a small, sharp peak. I didn't find that it bothered me much, but it did throw off timbre in those areas up top. Speaking of timbre, the LCD-2 did a better job at it, imparting not only tone accuracy, but also tonal weight. I did think the LCD-2s had a leg up in bass "detail" because of the imparted weight, but whether that's a part of bass detail or not is a matter of opinion. The HD800 had a leg up with presence and detail in the upper regions of course, as the LCD-2 is comparatively "shelved" there.
Spatial details were a step above the LCD-2, but not because I found the LCD-2's stage to be much smaller. In fact, I found the LCD-2s stage to be almost as competent in width and depth, but the HD800s edged it out in the vertical axis. Add up the z, x and y axis and the HD800s have a more enveloping, seemingly larger, definitely more three dimensional stage. It isn't like there's alot of spatial information in the vertical axis in a recording usually, but it's a nice thing to have.
With the right track going I can safely say I prefer the HD800 to the LCD-2 and would put them in a slight category higher, but given that I must eventually listen to some normal recordings the LCD-2s do it for me on a more regular basis. I didn't find the HE-500s on the same level as LCD-2 nor HD800, it had great tonal balance, but not enough extension, some kind of hump in the bass that led to lack of bass definition and resolved zero spatial details. Ok, almost zero. At least compared to these two phones.