I have the HD580 headphones, which have the same drivers as the HD600s. I've had tube amps that I enjoyed very much. However, I had found that the bass with the tubes tended to be a bit muddy and it didn't have the slam, the pop that rock music demands. I had since moved onto solid state offerings. I had my M-Audio Fastrack Pro for over 10 years and whereas the DAC on it was pretty good, the amp wasn't powerful enough to drive my headphones. Rather, it could drive them, but there wasn't enough headroom. I have since moved on to Topping E30/L30 combo. The L30 can drive the headphones without any problems and there is more than enough headroom. I'm sure that comparable amps such as Schiit Heresy, JDS Atom and the like will do just as good a job. Furthermore, my phones finally have the bass slam and pop. These are not the fastest of headphones, so a fast amplifier really helps and that's solid state. Tubes sound glorious, but if you listen to rock or pop music, they don't quite cut it in the bass department. If you listen to classical or vocals, tubes will take you to a place from which you won't want to come back.
