I have the same card and distro although i am running current.
I have managed to almost get everything to work, i can now get sound through KDE and the KDE apps, also i can get VLC to work by selecting the card directly in the sound options but mplayer complains of no sound card and flash does not work.
To get sound in KDE go to system settings and then multimedia and on the phonon tab there is the option to set the preferred card.
Alsamixer is showing volume controls for the hdmi but as above i cannot get all apps to use it by default. Can you confirm that i just need to patch alsa or am i missing something else?
I have tried kernel 2.6.37 and 2.6.8-rc2 btw.
I have resolved my issues by creating a ~/.asoundrc file with the following