Most appropriate simple IP direct for Drupal 7
All of the modules you have listed only provide APIs, choose one for which you need least maintanence. For geoIp you need to keep updating County List DAT file manually once in 3~4 months, I am not sure about others. Once you choose your module you have to write logic for your scenario, something like this

$cc = geoip_country_code();
if($cc == "AU"){
  drupal_goto(MY_AUSTRALIAN_SITE_URL);
}


You can use page--front.tpl.php or make use of drupal_is_front_page() in page.tpl.php to write your own logic.