My website that is averaging +20,000 uniques per day & I'm looking for good CMS that can handel this traffic. I'm not sure about Wordpress but current Joomla will overload my server.
Try Drupal ...however..i know some people how run Joomla on sites with similar traffic with yours and they have no problem...
joomla does not overload your server. if your web site is using sef url and so many component, i suggest you to check it