Thematic Fourth Subsidiary Widget, above subs though.

gistfile1.php

// add 4th subsidiary aside widget, currently set up to be a footer widget underneath the 3 subs
function childtheme_add_subsidiary($content) {
    $content['Footer Widget Aside'] = array(
        'admin_menu_order' => 250,
        'args' => array (
        'name' => 'Banner Aside',
        'id' => '4th-subsidiary-aside',
        'description' => __('The 4th bottom widget area in the footer.', 'thematic'),
        'before_widget' => thematic_before_widget(),
        'after_widget' => thematic_after_widget(),
        'before_title' => thematic_before_title(),
        'after_title' => thematic_after_title(),
            ),
        'action_hook'   => 'thematic_footer',
        'function'      => 'childtheme_4th_subsidiary_aside',
        'priority'      => 1
        );
    return $content;
}
add_filter('thematic_widgetized_areas', 'childtheme_add_subsidiary', 50);

// set structure for the 4th subsidiary aside
function childtheme_4th_subsidiary_aside() {
    if ( is_active_sidebar('4th-subsidiary-aside') ) {
        echo thematic_before_widget_area('footer-widget');
        dynamic_sidebar('4th-subsidiary-aside');
        echo thematic_after_widget_area('footer-widget');
    }
}