I have believed for about 40+ years that most speakers/headphones sound better with more power and I expect the additional power of the Ember is what brought out the best of the HD650. I have a Sunrise II and I will probably pick up an Ember in the next couple of weeks primarily for the additional power.
A lot of people love the HD650 but many, including myself, believe the sound is veiled. I owned a pair but sold them after a couple of weeks. That said, I used them with a tube headamp and I might have like them more with a SS headamp. Not sure because I never tried it.
Yes it was. I picked up the HD598 which I really like but I'm still looking for a really great deal on HD800 or possibly HD700. I would get an HD600 but I'm not sure its much different than the HD598. I had the HD650 a few months ago and sold it. It was seriously veiled to me.