I'm just amused that the discussion was initially about what amps pair well with the HD600. I know the question was asked about neutrality - and for me both the NFB-12 & LD MKIV (while both having a touch of warmth) are still relatively neutral/natural sounding (depending of course on which tubes you have in the LD).
The next thing - the remarks start coming about neutrality for studio use - and that was never introduced or asked about.
AFAIK - we were discussing what was best simply for listening.
I also am really amazed at some of the snide remarks toward peoples preference. I personally like both SS and Tube. I'd never belittle anyone though that had a preference one way or the other. It's all about sharing experiences - even if you don't agree with other's perspective. Live and let live.