It would seem I was not alone after launching Amarok only to hear.... nothing!! dooooh -><-
For some reason the switch to GStreamer as the prefered Phonon backend under 4.3 has caused some issues as discussed here.
As detailed in the above post the following should resolve most issues :
pacman -S gstreamer0.10-plugins
That will install all plugins required. However some people are switching to xine which also appears to rectify most problems.