I just want to report here a few things regarding audio:
1. I've managed to get both the iBasso D12 and Head Amp Pico to work with my S3. They sound just as they do when connected to a laptop. If you connect a DAC to your S3, the phone's speaker should go silent. If it does and you still get no sound out of the DAC, disconnect everything and try again.
2. The stock headphone jack is too noisy for use with IEMs (inner ear monitors). It sounded OK to me with full sized headphones though.
3. I'm on Blackstar, which retains USB DAC support. I'd expect other Touchwiz based ROMs to do so too. Sadly, I haven't found any AOKP ROMs that do. I seriously hope that someone ports the relevant drivers, as I want me some CM10.