Recently, I created a bare-bones design for TI's PCM2707 USB DAC. This was the first time I designed a board layout. It was enlightening, to say the least. The board is almost entirely surface mount and comes in at a hair over 1 sq inch. I have five of them on order at BatchPCB - I'll share the schematic and layout for this one once I get a chance to play with the hardware.
Once the basic board works, I would like to make two derivatives - one bus powered with a headphone amplifier, and one self powered with a heftier amplifier. I have not decided on a specific amplifiers yet, but I am considering the 25 watt TAS5713 for the board with the bigger amp. This chip sings from an I2S input, which should help keep a short analog signal path.