HD800 newbie here. With a quick story.
I borrowed a set from a friend a couple of months ago and tried them with my assortment of middle range amps (Audio GD SA31, Lyr, DV337Se and etc..) and a few vintage receivers and liked them very much, but did not fall in love like the first time I heard the HE-500 or the Lcd-2s
While in Denver, attending a horrible business meeting, I heard the HD800 on his amp and my jaw dropped.
His setup was a Bitfrost uber (hey, I have one of those) into a Fosgate Signature amp, I was stunned. The exaggerated treble that I heard from them with my gear turned into detail, the mids that I did not hear on my equipment turned into liquid golden mids that had me close to tears, and the lack of bass turned into the tightest most precise bass that these ears have heard with any head phone. Needless to say I now own the same amp and HD800 and as close to the end of this quest as I have ever been.
I am sure I am preaching to the choir, but when I read about how proper synergy between the amp and the HD800 is crucial over and over I shrugged it off and assumed it was over- exaggerated, it is not. The HD800 is just an incredible sounding HP.