hmm except for huge soundstage I prefer the opposite kind of sound for classical- rich and euphonic. Best classical music headphones I have ever heard, and maybe the best I have ever heard classical reproduced was with my Headphile HP3000- warm but also fast and detailed.
I'm thinking acoustic and vocals is where the K501 does best. Genres that don't require (as much) lower mids and bass.
The K501 indeed excel with acoustic venues and vocals. It's their cohesiveness coupled with their expansive soundstage and midrange integrity that, for me, help generate their "magical" rendering of period/baroque/classical pieces.
But I do agree that with larger scale symphonic works, like Bruckner for instance, I will often reach instead for the DT880/600, which bring timpani, bass and bassoon to better bear, albeit with compromise to the midrange.
Never climbed any higher up on the Grado ladder than the SR-325i, so I cannot comment on the HP3000, let alone the Headphiled version. Would like to hear them someday, though.
For acoustic jazz and raw/close-miked vocals, though, the K501 are unquestionably--even reflexively my--"go-to" headphones.