I heard them with both of them, but very brief with HDVD800 and I think Conductor is better overall ( and it sure has a better dac implementation ) . With Conductor you can drive any headphones. With HDVD800 that is not the case from what I heard (Audeze & HDVD800 = disaster)
While I am glad Darku rendered a review of the HDVD 800, it would have been a bit more informative if rendered in English. I know I have seen him write in English before.