If you can build custom sites with Joomla and Wordpress then Modx will be easy... not that complicated at all and there's a great community over there.
Have a look at MOdx.
Researched them all and Modx is great! Ajax, internal SEO, no outdated systems...
Joomla, Drupal and wordpress are not ideal for designers building in their own designs... takes too much effort if you don't have tons of time