Do you have a minute?
I don't own the HD-700. I had an hour or so to demo it at my local hi-fi dealer as they were willing to give me an unbelievably good price on the headphone. Unfortunately I had to listen to it on a Yamaha AVR, which I guess isn't the greatest thing out there to do the HD700 justice. I'd imagine a tube amp would do nicely with the HD700.