Hi Matt:
How's the golf ?. I spent an hour and a half with the Crack and the HD 800. Please note that my Crack is about 3 hours old by way of use. I thought the overall sound was elevated. Don't know how to say this but the bass is still not reaching the deeper extensions that my Zana Deux is achieving. In addition, I noticed the noise floor between songs which I don't have on the ZD. I have moved the Crack to a place where I believe it will be relatively free of noise due to other equipment.
Interestingly, I found the HD 650 to be a much better pairing from the get-go with the Crack. I am going to persist with my Crack and 800 pairing and see where it takes me.
Fitting a choke and replacing the last electrolytic capacitor with a film capacitor makes a nice improvement to bass extension.