Box for external PCM2704 USB DAC to S/PDIF Sound Card Decoder Board that you can buy cheap at ebay.com
Attaching to Raspberry Pi you can get much better analog audio output (3.5 jack connector) AND digital SPDIF output that you can plug into your receiver via optical or coax connection.
Therefore you can get highest quality multi-channel sound.
Tested with Raspberry Pi 2 and KODI/OpenElec image. Sound card is really plug&play, no additional setting is required.
You can of course connect it to any other device (e.g. laptop) using USB interface.
50 - 100%