I've just completed such a project. However, I didn't bothered with the hipsterish CMoy headphone amplifier.
My implementations uses a TDA1308 (recovered from a desktop PC CDROM) in an inverted, half-VDD-polarized configuration, straight from the datasheet.
Power is supplied by a single slim LiPo battery charged by a MAX1555 equivalent that I have both recovered from a car Bluetooth unit.
In addition to the audio/power circuitry I also added three buttons with some resistors that implement the Main/Vol+/Vol- commands for my new Xperia Ray.
Cheers,
Dan