It is possible to play video and audio files using amarok and kaffeine. What you need to do is:
1. Install win32codec and mplayer packages from the pacman repo.
2. Update the xine and amarok package (as noted by thorkelljarl)
3. To play audio in amarok change engine to xine
To play dvds in kaffeine and other applications (other than vlc) you will need the libdvdcss library from videolan. I think you can get it from the repos but here is a link: http://download.videolan.org/pub/libdvdcss/1.2.9/rpm/
What is good about vlc is that it is an all in one solution for both audio and video, but installing win32codecs, mplayer, xine are integrated and will allow you to use other multimedia applications that rely on them.