Regarding your "portable" rig - I'm also impressed. You've left the plantation in search of good sound - sacrificing convenience for quality - which totally rings my bell.
I've not heard the Geek Out yet, but it seems everyone thinks they sound great with the HD800. Are you using a CCK and a USB "Y" cable to supply the GO 450 with only data from the CCK and power from the Anker battery pack? If so, which USB "Y" cable did you get for this purpose? And which Anker pack are using?
Can you post a picture of this contraption? I know it won't be pretty (except maybe to my eyes.)
[size=1em]I was a beta tester for the OPPO HA-2, which makes getting even Hi-Res content off of an iPhone very convenient and tidy - smaller package, fewer cables - but its amp section doesn't offer as much power as even the GO 450, much less the GO 1000, and even though the OPPO HA-2 uses the same ES9018KM2 DAC as the Geek Out, I do [/size]
[size=1em]not [/size][size=1em]like the way it sounds with the HD800 - it's too bright and has that same ESS "glare" and brittle treble that I hear in most other 9023 and 9018 implementations. Add to that the very neutral, Class AB amp section of the HA-2 and it just doesn't work well with the HD800.[/size]
Again, having not heard a Geek Out, I suspect it's the warmth of the GO amp section that is responsible for its success with the HD800, but perhaps it's also a matter of LH Labs' implementation of the ES9018MK2. I would love to hear your comments on this (especially if you've done any Line Out testing with the GO to a known-to-be-neutral amp.)