I think that you're right ac500. There is no possible way that my HD-650 can equal the HD-800 and I will not make any claims as such. Truthfully, the HD-650 is a place holder for me right now. It reintroduced me to the Sennheiser sound after many years and I like it a lot. I think the HD-650 represents a stellar value especially if you can buy it used and in mint condition.
I have no desire to post in the Sennheiser HD-800 appreciation threads. It's a $1,500 USD headphone and I plan to get a $816 USD Cardas Clear cable for it on top of it next year in 2013. I can afford it right now, but I don't want to think about it for a while.
I was told by Pigmode not to change up the rest of my audio system before or after I get the HD-800 because it developed polarizing opinions by owners. I think that I will heed his advice.
I am done talking about the HD-800.
The HD-650 is the most tonally balanced, neutral, accurate, and pleasant sounding headphone that I have owned in a very long time. I can hear changes that I make to my audio system upstream such as when I had the Audioquest Diamond 1.5 meter USB cable or when I got my Audioquest Cinnamon 1.5 meter USB cable which I am using right now to connect my System76 Bonobo Professional laptop to my audio system. The HD-650 is the most comfortable headphone that I have worn in a long time too. I can listen to my favorite music using them for several hours without fatigue. I was listening to my music all day today to stay awake during the day.
HD-650 represents an awesome value by today's standard. I still think that these are reference grade headphones especially with an aftermarket cable upgrade such as Cardas, ZU, Moon Audio, Jena Labs, etc. These are no longer the current top of the line reference grade headphones from Sennheiser, but they are a damned good value for the money and sound. I can see myself owning them for quite some time before I decide to upgrade to the HD-800 with Cardas Clear cable next year.
These HD-650 headphones have made me stop looking for another pair of headphones or earphones for a long time. I can live with them for another year before I upgrade to the HD-800 with Cardas Clear cable.