780G chipset sound output through HDMI
All drivers were installed correctly and the onboard sound was disabled.
But when viewing the supported formats for the playback device, it only listed 2 channels. Unfortunately I have been unable to change this, although I have got full 5.1 DTS and DD sound coming through to the receiver, by selecting S/PDIF pass-through in all the applications (even through I was using HDMI, not optical). The only problem with this is music comes through stereo only as WMP doesn't pass-through stereo sound through as 5.1 in anyway and foobar doesn't support pass-through, although there is a component you can download, but this wouldn't work for my sound card as I think the DVD-A disc rips are 6 channel rather than 2.
I think the only way of getting proper 5.1 surround sound out of music, will be to buy another sound card and use another audio input in to the receiver.
Driver wise, I used the latest Catalyst package (9.6) and the Realtek ATi HDMI Audio driver (2.28). At this point I would also like to point out that the download speed from Realtek is diabolical. I ended up getting the filename of the file and searching on Google to find a mirror. Don't be fooled by the other driver download sites, as they just directly link to the Realtek driver rather than a proper mirror.