I own the hdvd800 and the hd 800. The amp and headphone is a killer combo. Now the dac in the hdvd800 is ok to nothing great . But a good start . With my offramp or AP1/PP THE Combo is much better. For whatever reason some people here just dislike the hdvd600 or 800. PM me if you wish to ask me questions . Or in the open forums .
I can vouch the amp is the best or one of the best
For the hd800 cans. The DAC in the hdvd800 is ok as well but greatly improves with a
AP1/PP or offramp 5.
But given the cost and looking for an endgame rig
I would get the hdvd 600 and a DAC you like. Balanced is a must for headphones
And DAC. My comment regarding the stax is based
On a MyTek DAC or msb and the above headphone rig as compared
To a stax. 009. I would do the hd rig and save plenty if money
Ask me questions and I will give you my perspective from an owner point of view
Not a reviewer.