Well, that kind of forecloses your options if you mainly decide on getting something that you had before. And, reading between the lines or just trying to read your mind, I guess you wouldn't be asking the question
at all here if you were extremely satisfied with the HD800s.
But listen, I've had HD800s for 3+ years (2 pairs of original and newest vintage using several different cables) and I have to say I prefer the HE500s (all with the same upstream systems).
So I will go out on a limb here and suggest you take a risk and get the HE500s. And with the $$ you save you can pick up a Moon Silver Dragon cable for the phones and add that marginal goodness
that really propels them upward.
Ha, this is headfi, there are few here extremely satisfied with anything for very long. You seem to be an exception. The lack of LF impact was what drove me away from the HD800 but that was when I had the Concerto and vDac so am hoping they will do better with my current rig. I'm very interested in the HE500 and have updated my FS listing to reflect that I am open to trades (+cash) for either the HD800 or HE500 however the HE500 is pretty hot right now and I'll probably be hard pressed to snag a used one in as good of condition as my LCD-2's are but who knows. The things I've read about the HE500's rendering of vocals really peaked my interest. My favorite instrument is the female voice