Hi,
If you have the latest version of Card JX for 1.5, than basically all you need to do is to install Card JX on your new Joomla 2.5 site, and than copy the contents of the database tables _grids, _grid_conn, _grid_columns to the same tables in your Joomla 2.5 database. Of course you have to be aware that there is a different table prefix on each Joomla installation.