[bmichels]

I think that for real portability I will finally end-up early next year with :
 
Samsung Galaxy S3 + Firmware patch to support 24/192Khz USB output + Centrance HiFi M8  + balanced Headphone
 
(Or Samsung S4 when available because of it's 128 Gb internal memory thanks to the 128 Gb Samsung chip already in mass production)

 

[Golden Ears]

Lynx Hilo  can run off of AC or DC battery.
 
Mostly likely better sounding than the rest- but only transportable, not portable

 

[m-i-c-k-e-y]

Sony PHA-2
 
Link: http://www.head-fi.org/t/680208/sonys-dsd-capable-pha-2-portable-headphone-amp-dac
 

VenturCraft Soundroid Typhoon

Link: http://www.head-fi.org/t/663590/venturcraft-soundroid-typhoon
 
All can do 24/192, DSD, cross platform capability and battery operated.