here's what to do:
Install all the pulseaudio stuff. "padevchooser" is very important.
uncomment this line: default-sample-channels = 2
and change the 2 to 6 (for 5.1)
go to KDE Preferences -> Multimedia -> put Pulseaudio to the top
start padevchooser, go to Configuration and change the profile to your need.
if padevchooser has lack of icons, take a look at this
You also have to uncomment this line:
enable-lfe-remixing = yes
otherwise the Subwoofer gets disabled, when you skip a track at amarok or something like that.
when everything is fine, you can disable the automatic startup of padevchooser, it's not needed anymore. (But you can manipulate the output-volume of every program with it, so its your choice)