I've been using MODx lately and I have been loving it. It's very easy to customize. It doesn't use "themes" like most other CMS. It uses CSS templates.
You simply insert chunks, snippets, or template variables into the CSS template like:
<div id="header">
<h2>[(page_title)]</h2>
</div>
<div id="content">
[*content*]
</div>
I'm not good with php, but if you are, from what it sounds like, you can make it do pretty much whatever you want very easily.