Really want to try a planar magnetic. Unfortunately from what I've heard, they don't have a large enough soundstage for genres like classical music.
I personally like the HD 598 myself. Slightly lacking in bass quantity for Bach, especially in contrapuntal passages, but they have the most realistic soundstage I've heard. Great midrange (perfect for cello) and treble is not fatiguing. When I listen to organ or symphonic musics with a lot of high frequency sound, I try to EQ the treble down very slightly, to render a darker presentation. For every other genres, I prefer to leave the treble alone though.
For classical music, I'd recommend a speaker for best sound though. If you really need headphones, you should look into ones with open soundstages (Q701, HD 598, AD-2000, etc.). Beyerdynamics are alright I suppose but still feels claustrophobic in comparison to the 598.