Google suggests that amarok doesn't support video playback currently but version 2 will do so. *linux.wordpress.com/2007/03/13/the-road-to-kde-4-amarok-2-development-is-underway/
But, there's a way around *www.kde-apps.org/content/show.php?content=41435
It's a script which calls Kmplayer from amarok, you can edit it to call any other video player as you wish too.
Give it a try and see.