Koss Pro DJ 100 / Tony Bennett (I now have both!)
I like it's nice and full mids, good low bass and lack of an annoying mid-bass hump. It's treble is also very smooth to me.
Strangely this has benefited more from amp/dac changes than my Q701 and K400. About as much as my HD-650. Call me nuts if you want!
If I had to live with only one headphone this would be it. Oh yeah, despite the ugly graphs, I find it to have slightly emphasized upper mids (like a Grado!).
AKG Q701
Better sounding than the Anniversary, K400, K501, Sextett and K601 IMO. If this didn't exist I'd keep the K601 or K400 with K601 pads.
Possibly the only perfect headphone I've owned. Not even my precious DJ100 is perfect (stupid pads!). I think it doesn't need any more warmth or stupid bass.
Sennheiser HD-650
This one sounds very flat and has just a tiny bit more low bass extension than my Q701. No mid-bass hump or lack of treble here.
It does sound warm, but not too warm. The HD-600 definitely had more mid-bass. Weird. I had two pairs a few years back and they were dark and had more mid-bass.
Maybe I have a crappy pair
I love it though. I gave this headphone a second chance after not liking the old pairs. Not sure what happened. Same gear mostly.
Sennheiser HD-598
Amazing soundstage but the sound is grainier than the HD-650. I've found it to have more treble and to be a little more detailed.
It's smooth sounding yet still fun and energetic(!). I especially love it for female vocals. They do sound more forward and clearer though on the Q701.
Since I have the Q701 and prefer that, this gets almost zero use. Mine is recabled with Mogami W2893. Yes, it was worth the $10
I don't think this is at the same level as the HD-598, but I love how easy it is to drive.
AKG K400
I generally find it to be a bit thin with my setup. My amp isn't warm or cold really. To get past that it does sound better with K601 and K702 pads.
It's the 2nd headphone that actually WOWED me when playing acoustic music. The first was the ATH-AD2000.
I actually think this has more treble than my Q701! It does have a larger soundstage too.
KRK KNS-6400
Not enough time to listen to this. I also had the 8400 but accidentally destroyed it. Oops.