Sennheiser or Beyerdynamic?


Max budget $600, non-wireless, open back. I own a Benchmark DAC combo-headphone amp. Comfort important, but sound is more important. 

I’ve heard good things about BD’s Amiron home model. Also the Senn’s HD660. Anyone done an A/B shootout or own both?  I’m into hi rez digital and DSD music of all kinds... mostly pop/rock/folk/vocals and natural recordings of acoustic string instruments. Also Jazz and Classical. 
128x128rocketroom
Lol @ Ken Rockwell.

If you want to keep some money in your pocket, get the Massdrop Sennheiser HS-6XX. At the high end of your budget, get the Massdrop Focal Elex.
the blon b20 ($450 on massdrop) are open-backed planars, very comfortable and sound great---not a western brand but would be my pick in that range
Thank you all so far for your replies. Really great info so far. So glad to be a part of the AG community!
BD DT 990 PRO’s perfect for longer listening sessions. Very comfortble and a non-fatiguing pro sound. I change to AKG 701Q when I like to have a closer look at a specific sound or instrument. A little sharper but also not as comfortable and fatiguing (for me). DT 1990 may be a fine all-round choise. Don’t forget the Philips Fidelio X2 if you can find one. Mucho appreciated in this price range.