PulseAudio is installed by default, but somehow the built in GUI to adjust the sound card preferences does not work, or in my case does not save the preferences. This means the internal sound card is always chosen as default after a reboot. I tried to modify the respective configuration files manually, but the following is the better option:

apt-get install pavucontrol

After that, run the control panel and disable the conflicting built in audio hardware.

Run Amarok and play a music file to check the changes have been successful.