Well, I think I resolved the issue...or at least improved the situation.

Xeons comment about overheating made me start looking in that direction, which lead to me finding that my system was trying to push the sound through the GPU as well, so switched that off, disabled and killed literally every non essential service and then lowered my graphic settings.

I have not put it through any long term stress tests, but my 60-90 minute game sessions yesterday were all much more stable.

Thanks for getting me pointed in the right direction! Love the game so far!