I am using Ubuntu and XMBC on my HTPC and have chosen the Radeon HD5570 Video card which has an HDMI output. In the sound preferences there is no surround sound option for the video card just stereo and although I can get sound through it in XBMC, my receiver does not state Dolby Digital on movies that are in fact Dolby so its definitely not giving me the true sound it should.

Does this card not support surround sound through HDMI and I somehow missed it? If that is the case does anyone have suggestion that has been tested and works? Id like to know its going to work before investing in yet another video card.

UPDATE

I purchased a Nvidia GeForce GTS 450, plugged it in, downloaded the proprietary driver from the system control panel, disabled the onboard audio from the BIOS (not sure if this was necessary but I did it anyways), and changed the sound settings to use the new video card. Everything works flawlessly. It was a seemless setup.