Consulting on Architecture for 5+ server Joomla/MySQL Website

We have a mature Joomla website with thousands of pages and 70,000+ active users. The site currently has 1 MySQL database server with 5 CentOS/Apache servers and a load balancer. The load on these servers is much higher than it should be and the site has performance issues frequently. We're looking for an expert(s) in high end CMS/Joomla websites to review our Apache settings, MySQl setup (add High Availability and or migrate to a more scalable database) and setup with CENTOS and Rsync. We have one main server our bloggers and content contributors publish to that replicates to the other 4 web servers. We use a cloud platform to replicate and backup servers. We use Rack space for file storage of images, power points and videos and we are open to switching this to a different CDN. We offer religious and family teaching resources. We're willing to migrate from Joomla to Wordpress or Drupal if need be, but need the best setup for scalability, reliability and growth including GEO redundancy. If you have expertise with fault tolerant web applications like described above we are looking for you. We're looking for a consultant that can either design or enhance our existing architecture and if you can assist with the technical work to make the needed changes even better.