I don't know about the Aeon or this Ether CX, but I believe that it blows the HD650 out of the water. The HD650 is the most overrated headphone of all time. It's way too colored, the muddy bass and bass bloat is unacceptable, and it is downright awful with fast tracks. I suppose is you listen to opera or classical, it might be ok as seems ok for slow music
I was also not impressed with the 6XX. Perhaps I had too high of expectations here though. It was only a $200 headphone new from Massdrop after all.