Too many sound devices enabled, they can conflict and cause problems. If you have on board audio enabled and a separate sound card they can conflict. If you are using a separate sound card, disable the in built audio in the BIOS.
For the Video card, are you using the correct AMD supplied drivers (and Catalyst Control Center)? If not, download the latest for your card at www.amd.com
The HDMI audio usually will automatically set itself as the default audio playback device (what is needed) if an HDMI cable is plugged into the video card's HDMI port.