dpkg -l | grep imagemagick
will show you the installed version
apt-cache policy imagemagick
will show you the installed version and all versions available in the repositories. consider that you need to run apt-get update first, to be up-to-date. also consider that you need to have corresponding repositories enabled (e.g. experimental)
regarding the "check upstream version", you would basically need to check your installed version against the "upstream resources" (probably project website or their repository -cvs/svn/git/...)