bob-b,
Myself rather new to headphones -- more out of necessity. I listen to jazz, vocals and rock (U2, Bruce Hornsby; nothing really heavy).
My decision to buy the DT990 (250 ohm) new model was based on limited testing (about 4 hours or so, over a few sessions) of the following: DT880(2006), DT990Pro, DT990(2006), Senn HD650, AKG701, Alessandro MS-1, MS-2. Auditioned with the Benchmark DAC-1. All the Beyers were 250 ohms. I do NOT consider myself as having critical ears. I can't give you a review that dissects the sound of each of them, but only generally what I liked and what I didn't.
The Alessandro's just did not do it for me. More authority with the DT990. Bass was more weighty. And it was very well controlled. I was told after I had dismissd them that the Alessandro's do very well for opera, but that's not my genre.
The DT880 were the ones I had initially thought I'd get, but as I switched between the 880 and the 990, I could not detect anything that the 880 did better than the 990. Depending on the recording, the 880's bass sounded OK to a tad weak. The 990 did not have that problem. Even on Jennifer Warnes' The Hunter (which I consider a somewhat bass-heavy recording), the 990 did not come across as boomy. It just managed to make things enjoyable, packaging the entire music very well. NO kidding! I never considered myself a basshead (and still don't) but well-done bass is so addictive -- and it becomes mesmerising when it integrates seamlessly into the rest of the frequency range. The mids -- all I can say is that it is done just right -- the tone and timbre of the voices, piano, guitars. And the highs -- there is a sparkle there, not sharpness.
End of the day -- I stretched my budget to get the DT990 instead of the DT880. No regrets.
I remembered trying to hear how much better the HD650 and AKG701 were compared to the DT990, but could not really tell. Sure, there was a difference in overall presentation/signature, but I think these headphones are at a level where they are all good and it's more a flavour already (and again, I don't have critical ears, so I may not hear what others may hear). I suppose I'm fortunate that the flavour that I like is by far the least costly of the trio here.
Last words? I find the DT990 to be a very good all rounder with a well-controlled and fun bottom-end. I was afraid that the treble might be sharp, but that did not happen to me. The top-end is clear. I am certainly enjoying it immensely. The only thing I wonder about now is whether I would have preferred to have the aluminium case of the old model rather than the current soft leather case. But then again, I don't foresee myself taking it places and the foam cutout in the case protects it pretty well as is.
Let us know what you finally plonk for ..... and happy listening!