Looking forward to reading that. There's no question you've heard the HD650 at its best and will present a balanced comparison. With the exception of impressions of the LCD-2 or HE-6, I'm quite wary of the hyperbole laced proclamations of such and such ortho putting the HD650 to shame. The lower tier orthos seem to be getting a lot of attention lately and it's been stated and now regurgitated by those who haven't even heard both, that the HE-4 blows the HD650 out of the water. Personal preferences aside, I suspect those making these comments haven't heard the HD650 through components that do it justice. This is from a Headfonia article on the HE-4:
Now the HE-500 may be a more substantial upgrade to justify the expense but the HD650 comparison towards the end of this article gives me pause. Some selective quoting:
Seems like the LCD-2 is the only way to go for someone who loves the HD650 in the first place.
I'm not sure why people bother to compare the HE-4s or any of the Denon headphones to reference headphones like the HD650s. Those headphones aren't trying to achieve reference sound. The whole comparison is arbitrary and pointless.