I just want to put in my thoughts between the two, I also prefer the HE400.
I think the 65th Anniv. bass has little emphasis that gives it a minor punch that is adequate for most circumstances. The HE400 bass is more satisfying though especially for drums and no matter in which bass part, it hits well.
The main reason why I enjoy the HE400 more though is that I find the HE400 does better with image separation. The 65th Anniv. instruments seems to be closer together, so I find them to be harder to track instruments in busy passage especially when vocal is present at the same time. When that happens, I find the vocals and the instrument seems to be fighting to see who is on top where as with the HE400, I can clearly hear vocals in it's own space and also each instruments, but still integrated as a whole. Not sure if it's just a trait of the HE400 or not.
I have a tendency to grab the HE400 more often for music listening, but occasionally grab the 65th for movies due to comfort from both weight and softer pads. The 65th is just light as a feather compare to the HE400.
this is my experience with owning both.