I know i'm late to reply to this, but i'm bored.
It seems to me the main problem with 75% of the headphones under $75 is that they're not very clear sounding. There's a few small exceptions like the DT-235, KSC75 and a few others. Some of them are so highly praised here, yet IMO sounded like muffled crap. I won't mention which ones. Headphones under $30 are especially bad. The best i've tried though (other than KSC75) is the Koss UR-22V, which is easily found at Wal-Mart. Some may not like it though, but for $20 it's pretty good.
The DJ100 is crystal clear to me. If it ever isn't it's due to a source or amp that's too warm sounding or other issues. Usually if something is making it way too bassy (Which is rare). Same thing if there is something in it's signature that sticks out too much. The mids on these with my current setup don't sound all that much more forward than my HD-598 and HD-650. They're certainly not even remotely laid back though.
Some have said the DJ100 has too much treble, yet others say it doesn't have enough. Hearing people say it has too much is just absolutely bizarre to me. It does have more than every Sennheiser I have, but not it's like K702 or Grado like treble.
I do find the bass slightly above neutral. It definitely has more than my HD-650. I guess my new HD-650 is pretty much close to being very neutral in the bass. This crazy pair doesn't even have a mid-bass hump at all.
The DJ100 certainly isn't some flat studio monitor, but I would call it balanced mostly, but with slightly forward mids and a tad extra bass.
I don't know how Koss managed to give a headphone slightly emphasized bass, forward mids and still manage to have enough treble. That's usually impossible. Can't have it all usually. I think they do make some harsh music sound a bit easier on the ears. Maybe theres some slight dip in the lower treble or something. To me it's as fatigue free as the HD-650, but a lot more fun to listen to. I bet the creators of the DJ100 must have been fans of the Sextett and HD-650. I really would find it hard to believe Koss just picked some random import and called it the DJ100. I mean it's too good.
Never tried the DJ100 with a tube amp, but maybe someday. I'd like to try it with a cheap hybrid tube amp next year.
I haven't tried the DJ100 with any super expensive gear, but I will say that it has improved with every single upgrade i've made with my setup. Even more than my HD-600 and Q701. About the same as the HD-650. I know some here will think i'm nuts for saying this, but that's what I heard. I was surprised the ODAC didn't improve the Q701 further than it did. Yeah..i know there's some that think the DJ100 doesn't change at all..or doesn't even need an amp. My HD-650 actually sounds better without an amp
There's only two headphones I own that I refuse to use without an amp. The Q701 (K601 too I guess) and DJ100. I was really surprised how well my old Ipod 3G can drive the 650..
BTW I wonder if anyone has tried the DJ100 with the Schiit Lyr? Just read it has an output impedance of only .2ohm or something. Should be a good match for my HD-650 when I can actually afford a new amp.
I'm actually more interesed in how it is with the DJ100 rather than the HD-650