Most lightweight cms/framework?

Hi all!

The problem is the following: i have a site which is running on wordpress. My expression about wordpress is that it is really lightweight, but as soon as you try to extend functionality with plugins, it can be a really cpu expensive script, even with cache enabled. I'm looking for a light cms/php framework, which has the following options inbuilt:
- login/user panel, avatar and pm system
- maybe a forum
- good API, secure system
- highly extensible with custom code
- very good caching system, or maybe static pages as output.

Of course these things can be achieved in wordpress, but i would like to get these inbuilt, like in drupal, but maybe a more light system.

I hope there are solutions for this! Waiting for ideas! If you think that wordpress is still the way to go, post your opinion and ideas.

 

How about textpattern ?

 

well, i don't know much of that one, but as far as i know, mainly that is just a blog system too, so the user panel/pm system/avatar would be not that pretty to implement (and as far as blog systems, i don't have doubts that wordpress is the best among them). I thought of a cms like e 107, but a more "live" project, i mean e107-s development seems really stalled and is far behind new generation cms-s. Still, i like the concept (easy implemented forum, good cache, lightweight, good user system - that is what i'm looking for)