Spring RTS Engine

At the moment I use joomla for darkstars but its cpu intensive and thus pages load slowly.

Thus I would like to consider moving to another cms but which?

I intend to attempt to make the other cms look and behave like the current joomla site as much as possible.


So any ideas?

I've been using Drupal. I don't really like it, but it's popular.

PHPNuke is tried and true classic...