I'm glad I'm not the only one who likes these cans. I got them a few months ago and I was shocked at how good they were, and how much better they are than the 80 ohm version. I've written about it in the Zombies thread where he compares all the Beyers.
I have T1's, and out of my current setup, which is Musical Fidelity M1DAC --> Schiit Asgard 2 or Musical Fidelity M1HPAP --> T1 / DT770's, they're very close to each other. I would have never believed this is if someone else told me, but they actually sound 90% identical. I mean...like, in terms of detail, resolution, soundstage, balance, everything. The only differences are that the mid-bass on DT770's is bit tighter and punchier, but has less presence (T1's mid-bass seems softer but stronger), DT770's have a tiny bit more sub-bass, DT770's mids aren't quite as lush and smooth, and the imaging on the T1's is every so slightly more defined. DT770's sound pretty much as opened and spacious, and grand in scale, as the T1's do, and they're as detailed (I can't hear anything on T1's that I can't also hear on DT770's, in fact, sometimes I feel DT770's throw details at me more clearly). The biggest difference is that T1's sound smoother overall, in order to notice that, I have to listen for a longer period of time. Whereas T1's never ever make me feel tired or fatigued, DT770's sound does that a little bit after 2-2,5 hours of listening, which means that they're ultimately not as smooth. But otherwise, I would be perfectly happy to keep the DT770's as the only headphone until the rest of my life. It's truly amazing that I can listen to T1's for hours, and then take them off, put the DT770's on, and feel like I have headphones on my head that are not inferior, just very slightly different in the way they present sound. Having owned every Beyer in 770, 880 and 990 line ups, I'd say DT770 Pro 250's are overall probably the 2nd best headphone a Beyerdynamic fan needs to own at the moment (after T1's), and the 1st in terms of value for money. They just do everything right, build quality is amazing, sound isolation is amazing, they're very comfortable (especially if you stretch out the headband), they're not too hard to drive, and they sound amazing with all types of music. In fact, with most music, A-B comparing both headphones, I prefer the DT770's over T1's, because they sound more fun, vivid and engaging. T1's are more precise in audiophile terms, but DT770's are more fun. The only music I prefer the T1's with is some jazz, some classical and some vocal and instrumental tracks, but with rock, metal, pop, hip hop, electronic, dance, some jazz, instrumental and classical, I prefer the DT770's.
T1's can probably scale higher if you go for really high end amplifiers and sources, so ultimately, they'd get the lead over the DT770's, but if you don't plan to invest more than $1000 on an amplifier and about the same on a DAC, they're neck a neck most of the time.