I owned the Beyerdynamic DT770 Pro, DT1990 Pro and the DT880 premium for a short period. The DT770 and DT990, produced a bass rattle at very low frequency (heavy base, hip hop type music). I assume that the diaphram is not made for that kind of music or that I had a faulty device. However it seems to be a common ocurence if you google it. The DT770's are closed headphones, litlle sound stage, the bass is more pronounced / distorts slightly and overshadows the music experience a bit in my view. It is subjective though, some people like it. The DT990 is open, has good sound stage, great headphones but not made for heavy bass either. Also, you can't listen to an open headphones while the family is watching TV for instance. It leaks sound inwards and outwards. The DT880 is in between DT990 and DT770, it is said to be semi-open, nice headphones but are very flat, not dynamic enough for me. The T1 is great but costs 3-4 times more.
Some people in this forum may disagree but the best headphones in the R2500 range is the Audiotechnica M50x. I personally have the M70x, I listen to it straight from the iphone, it has 35 mohm impedance. It is very accurate, does not distort, it has a bit too much treble and it sometimes sounds non-musical / non-harmonious, too detailed, you loose the melody
. I personally like it, but some people may hate it.