Minor update:
I finally sat down and gave the DT880 with Millett Hybrid an extended non-critical listening session (the amp hasn't been used very much since I got it some weeks ago). I didn't have time to listen to the K701 too for comparison, sorry. Another day perhaps.
Equipment chain:
Onkyo CS-V720 > Radio Shack 18AWG RCA/RCA IC > Millett Hybrid w/ RCA 12FK6 tubes > DT880
Burn-in:
- Unknown amount of hours on the Millett Hybrid. Bought it used though, so it's probably well burned-in.
- DT880 is approaching 300 hours.
- Ok so the RCA/RCA IC is low-quality. I didn't have a spare so I pulled the one I'm using with my TV and DVD player.

Much better cables are coming in on Friday.
Zero 7 - When It Falls (multiple tracks)
"Warm Sound"
The bass notes get a lot more emphasis, so much that it reminded me of my former K271S which had an AWESOME bass impact once they were burned in. I didn't listen to this track much (it's not one of my favorites), so moving on...
"Home"
The lower bass rhythm gets extra power here too. It reminds me so much of my K271S it's just freaky.

The female vocal receives more detail than I've heard before, enough that I can almost hear the "microphone breath" (I suspect I'd fully hear it with a better source). The presentation is so rich, warm, and FULL. When all the instruments kick in at 3 minutes, the layers create a wash that's just a glory to behold. Warm, warm, warm, as expected - the DT880 responds to the tube amping incredibly well. Anyone who complains about the mids being recessed on the DT880 needs to hear it with a tube amp.

"Somersault"
The presentation on Sia Furler's voice is like she's singing right into your ears - up close, intimate. You can almost hear her vocal chords straining when she starts crooning later on. The strings in the background are very distinct, kinda separate from the main mix, but very much there, with the presentation sounding as if they're surrounding the other instruments.
"Look Up"
REALLY kicking bass on the main bass line that would overtake the rest of the frequencies on lesser headphones, but the DT880 balances it out - giving no less impact of course, but the upper frequencies definitely have a "come out to play" presentation. The strings are lush and have some of the upper-harmonics that strings are known for (which I hadn't really heard from this track before). The guitar action that interplays with the bass is quick and detailed. The harmonica-lead is very upfront.
"In Time"
I kinda stopped paying critical attention with this song, instead relaxing more to it. The female voice just caught up with me and entranced me with its sultriness.
Conclusion:
For me the change with even a Millett Hybrid was astounding. I had no idea the DT880 could change personalities as much as it did. Kinda bright and thin sounding with my solid-state amps (even with Zero 7), then it got all warm, thick, and mellowy with the Millett - just like my K271S. Made me miss 'em.

And for anyone concerned that the DT880 has no bass, well this amp proves them wrong!!!
