Bypassing internal DAC, etc on iPad and iPod Touch

I am interested in bypassing the internal DAC and headphone amp in these devices, and sending a pure digital signal to an external device to get significantly better sound.

I plan to listen throughb good quality headphones.

One possibility I am waer of is using the camera connection kit/iPad to drive USB audio in devices such as the benchmark DAC1 USB or the DACMini. Both have USB input, a built in DAC, and headphone amps.

Does this approach BYPASS the interbnal DAC, etc, in the iPad or iPod.

Also what is the advanatge in using the Wafia transport, etc.

Quite confused.

Thanks