I recommend you install the various xine packages from Packman, and use the xine engine in your multimedia applications. This works not only for kde, but also other desktops. I have done this on fvwm2, xfce and icewm desktops, and it works great. (in addition to xine, also grab mad and lame).
Do you want RPM packages for any of these decoder?
Probably in either of these places: