I'm astonished anyone would claim the HD650 is "bad for classical."
I spent much of my life close to live performances of classical music, and the HD650s come closer to what you're going to hear in a live performance than anything out there.
Listen particularly to a good, modern recording of chamber music to prove this.
Again, everyone's hearing and expectations are different, and different instruments and recording techniques and concert halls and ensembles vary significantly in the sonic result, so there is no "universal" claim possible.
However, I can attest to the HD650 sounding extremely natural to me. I actually reserve them for when I'm going to engage in sustained, uninterrupted, focused listening. And to almost anything, not just the benchmark example of a top-notch chamber music recording of classical music. They bring out the best in any recording you can find, and are highly musical.
One simple test is you'll find yourself listening to them, even at higher volume levels to represent more natural dynamic range, for extended periods without experiencing any listener fatigue. Which is a very rare thing.