Wouldn't it be more correct to add the additional Logo like this in /includes/templates/sage/common/tpl_header.php
<div id="logo2"><?php echo '<a href="' . HTTP_SERVER . DIR_WS_CATALOG . '">' . zen_image($template->get_template_dir(HEADER_LOGO2_IMAGE, HEADER_ALT_TEXT, DIR_WS_TEMPLATE, $current_page_base,'images'). '/' . HEADER_LOGO2_IMAGE, HEADER_LOGO2_WIDTH, HEADER_LOGO2_HEIGHT) . '</a>'; ?></div>
Then in /includes/languages/english/sage/header.php add the following:
define('HEADER_LOGO2_WIDTH', '200px');
define('HEADER_LOGO2_HEIGHT', '70px');
define('HEADER_LOGO2_IMAGE', 'logo2.gif');
Don't get me wrong kobra, as I haven't looked at the "modified" tpl_header.php file in that template, but that looks more like a "quick and easy" way instead of the correct way.