The Pi-DigiAMP+ is an add-on board that includes a Digital to Analog Converter (DAC) and powerful 35w stereo amplifier. If you want to turn your Raspberry Pi into a working Hi Fi stereo, just add speakers and you're off.
You can use GPIO25 to connect an IR sensor and GPIO23/24 for a rotary encoder. Both of these parts are optional, but are broken out on the Pi-DAC+ for convenient access. Note: pins reserved for the rotary encoder and IR sensor can be used for other purposes if those add-ons have not been fitted and enabled by software.