Resolved Stereo audio only from HDMI

This may not be a specifically Windows problem but it is causing me a lot of headaches and I would be grateful if anyone can offer help or point me in the right direction.

I am installing an older Acer T690 desktop running Win 7 to use as a streaming computer. I have put a Sapphire 6670 graphics card with HDMI output in it to feed the HD TV. The TV is a Sony and it passes the digital audio component through to the amp via an optical cable. I know all this works correctly because I have tested it with other equipment.

The problem is that I can only get 2-channel stereo sound from the HDMI playback device. Everything appears correct, except there is no option for anything other than stereo. I have been researching this and it seems to be a common complaint with the AMD ATI driver this card requires. I have tried updating the driver and also updating the Realtech HD audio driver but nothing seems to make a difference.

Does anyone have a solution for this? It is slowly driving me crazy.

 

I have spent a lot of time and effort on this and I still don't have a real solution but I know more than I did and I have decided to abandon this thread and mark it solved.

I managed to get two audio set-ups working. The first is the original one via HDMI. I have tried every combination of driver I can find and whatever I do, I cannot get this to work with more than two channels.

I found an SPDIF header on my motherboard and managed to successfully connect an optical output to it. Windows sees this as a Dolby 5.1 audio link. When I test the speakers individually through Windows, I get all channels correctly. But when I try to play any 5.1 source material, it only comes out 2 channel stereo. I don't know what else to try so I have given up on this.