my next build: a SUPER cmoy.
comes with a charging circuit, custom high capacity battery pack, high grade audio caps (blackgate/elna seraphine) and wires (kimber/etc), RCA/3.5mm input, the usual 3.5mm jack for your headphones/iems, and a possible 6.3mm jack. the size is big enough to fit the category "transportable"... somewhat 2/3 the size of an O2.
already got a prototype. stay tuned =D