Hmm...
Source: Dissected iTouch/iVideo with OLED, 64GB flash, iModded
Amplifier: DIY cMoy with audiophile grade capacitors and dual OPA627, running off a couple of thin lith-ion batteries.
Have both the source and amplifier housed in a carbon fiber enclosure, not much bigger than the size of a small 2.5" SATA harddrive enclosure (twice the thickness is fine by me).
Headphone wise, any flagship IEMs or earbuds, like Ety's ER4S, UE's customs, or Yuin's OK1/PK1.
Sounds achievable.