I'm currently using the xine engine, but having a problem with ogg gapless playback, and thought I'd try another backend.  I tried to uninstall amarok-xine and replace it with amarok-engines, but xine continues to be the sole engine option in settings.
I've tried uninstall with the --purge option, renamed the .xine-config and amarokrc files, rebooting, but to no avail.  I just seems stuck on xine with no choice.

How to fix?

Basically the idea of multiple sound engines is on its way out. In Amarok 1 the xine engine is already the default, and other backends are available (e.g. Helix) but not as well supported.

In Amarok 2 we only support Phonon anyway.