Sim,
I recommend that you use Joomla & play with several very customizable templates made by Rocket here: http://demo.rockettheme.com/ . It takes too much time to customize Nuke templates to your exact specification.
Note: Rocket Themes are famous for providing quality products...
Once you've found the template you like than mod the css to look like your specifications.
First, Joomla is less Hack Prone to simple security mistakes made by newer developers. Second the templates @ Rocket Themes are incredibly customizable. Click on the Sporticus Battlefield Template on the site & then click features so you can see what the original template started out as just to open your eyes to the modding possibilities. It's a great CMS with a huge amount of functionality & mods created by serious developers.
PHP Nuke is awesome but it just takes much more time for high level customization unless you have a professional designer. First if your a standard HTML writer you gotta use the templates provided & spend time making a generic theme look slightly different or you've gotta learn a proprietary method of coding the page... Too much work on your hands unless you have very good skills with the product & then if your not a designer your gonna be spending months making it look decent.
* Ever noticed why there are so many profesional companies developing nuke templates and customizing sites?
Well, thats all I have to say about that (My Opinion Only)!!!