Carlos,
the K501 or the DT880 would seem ideal (if you have a powerful amp).
The difference between the two is that the K501 has a slightly more dynamic treble (more pristine sounding) and the DT880 has a better left to right soundstage imaging than the K501 (which has a slightly more hard left / hard right soundstage).
Between the two, the K501 is definietly more comfortable. For a little more bass and treble "oomph" you can replace the K501 cable for about $25 with either Belden or Mogami low impedance Quad cable.
Since you are into boroque, the K501 at about $100 used looks like a good buy over the $250 DT880.
It will all depend on the recording as to which you might prefer. Female vocals are definetly more silky and intimate on the DT880, though. But if you listen critically, you should find that the K501 does better triangles and piano high notes, and perhaps horns. For rock they are very close, with the DT880 having the better bass slam, if not extension. But, again, it will depend on the recording, and if there is any really low notes to beigin with. I find most rock to be bass boosted and treble bright, which either should mitigate.
Neither headphone should be fatiguing. But you'll be able to wear the K501 a lot longer.
I have not heard the K240S, but the K501 looks more comfortable.