Don't know if this will help at all but I had a very similar issue with a pre-built rig from overclockers. Playing a game and then suddenly a continuous sound glitch and then have to force a shutdown.
After trying everything I could think of I checked the asus website for the drivers and found out that there had been a sound card driver update and the one installed was from the supplied CD. Updated the driver and 2 years later it has never crashed.
Don't know if this will be of any help but just another option.