Just to let you know, I have got this to work pretty well now. Not sure exactly what made this work but I'm again using the latest Realtek HD drivers and after very much fiddling in the Realtek control panel I checked the 'Speaker fill' and 'Bass Management' options and voila! Also played around a little with 'Room correction' to enhance the sound.
I'm very much certain that I did test these settings before so I don't know what caused the 'working-trigger'. The Realtek control panel is just horrible anyways