In order to get the full benefit of both sound and video from a HDMI connection is if you use a HDMI TV or DVD/HD DVD Home theater system like Bose:
-dvd or BR/HD
-sound system
-speakers
All you do in connect it to your TV. I am not sure if they use HDMI yet though. Anything less and you are paying a premium just to use the HDMI cable for just Audio or just Video were DVI cable on average cost less.