Why no system sound as user...only root

[Markus]

Are you using alsa? You need it for aplay. This is my ~/.kde/share/config/knotifyrc:
markus@fujibox:~/.kde/share/config$ cat knotifyrc
[Misc]
External player=aplay
LastConfiguredApp=Konsole
Use external player=true
Volume=100

[StartProgress]
Arts Init=false
KNotify Init=true
Use Arts=false

You can also use Arts and choose artsplay as the external player. If the option is now grayed out, try changing it in knotifyrc to something like:
[Misc]
External player=artsplay
LastConfiguredApp=Konsole
Use external player=true
Volume=100

[StartProgress]
Arts Init=true
KNotify Init=true
Use Arts=true