Before when you were using superuser mode, were you logged in as the root user? This might be why your sound was working as well.
If you created a new user with this new install, instead of using the root user, then your sound shouldn't work because only root has access to /dev/dsp*. Log in as the root user to see if your sound is working.
A quick way to fix your sound so that all users can use it should be to do a: chmod ugo+rwx /dev/dsp* Must be root or su to do this. There is a better way such as employing a group called audio, and putting audio devices in this group, and allowing certain users access to this group. If you want to find out how to do this, then search this forum, I've mentioned this before, several times I think.
I'm not familiar with KDE at all, so I'm not going to be able to help with the superuser mode.