I have a 27 inch iMac that I am using for a monitor. It is hooked up with a Displayport to Mini-Displayport cable. I use the GTX 660 as my graphics card.
The audio works with voodoohda or HDMI DSDT edits.
The problem is is that when my display sleeps the audio stops.
In Mountain Lion, I never had that issue. But for some reason in Mavericks I do.