It's just baffling to me because your the first person i've heard from who's ever said this about the HD-600. I seriously don't believe this is the general consensus. I've heard the K702 and DT-880 be called thin, but the HD-600 I guess if everyone here agrees, then you're right. I just haven't heard this before. It's kind of a shock! Doesn't matter that much to me. I now hate to see what you'd think of the HD-598!
Getting a tube amp just to warm up the sound and add weight to the HD-600 seems kind of silly. I could understand the K702. Of course I'm sure those aren't the only benefits. Actually this isn't so silly since i'd like to buy a hybrid tube amp for my $50 DJ100
I guess i'm abnormal because (IMO) adding any more thickness to the mids of the HD-600 would make them a muffled and congested mess. Hmm, maybe not. Probably depends on the amp.
BTW does anyone know if the HE-400 is warmer than the HD-600? I don't even know if they have any similarities. If it's as warm as the HD-650 I probably won't like it.
NOTE: This isn't a big deal to me. Not trying to argue, It's just that hearing the HD-600 being called thin weirded me out. Never heard that. Maybe I need to hang around in this thread more.
Thinnest sounding headphone I ever heard was the Koss A/250. I think that's the one rare headphone that almost would require a tube amp for me to like!
Everything in this hobby is relative; if someone likes the planar (HFM/Audeze) sound then HD600s will sound thin to them, simply due to the lack of bass robustness relative to planars. That doesn't mean HD600s are objectively thin, it is just faster-sounding than planars due to its voicing.
HE400s are warm but laid-back, with a strong emphasis on upper treble. Peculiar, I know, it's puzzling trying to describe its colouration to people who have not auditioned it in-person.