I just want share my experience with the DIGI+ in the hope that others benefit from it. My attempts to get the DIGI+ working with RaspBMC always ended in a disaster, i.e. after upgrading the kernel or enabling the external sound card, the system would not boot any longer nor react to anything such that a new installation was then needed.
However, the OpenELEC 4.1.6 worked out of the box, i.e. no updates needed at all. I simply needed to do the software configuration as described on the HP (only the location of the config files are different than the standard ones). Looking a bit further around one quickly finds instructions on how to move /storage to a USB drive which expedites execution by quite a bit.
At this point I am really impressed by this system! Many thanks for making this possible - I never thought that such an old ancient piece of hardware like the Pi is capable to deliver such a performance, i.e. high quality audio and HD video.
Success with OpenELEC 4.1.6