hello

i want to create a website that is easy to update from "admin".
i need a wysiwyg editor and the ability to update images, add testimonials and so on..also seo-friendly urls would be nice..i don't want anything too complicated since the design is already done..thanks

What is the theme of your website means either it is a shopping cart site or any news website?

for shopping cart - osCommerce is best
and For any news or information holding website - joomla is best.

I would recommend wordpress. It is friendly and a lot of extensions.

joomla is the best

If you're not familiar with the various open-source CMS systems out there, I would recommend using Wordpress. It doesn't have all the features of other CMS systems, but it's definitely the easiest to use, and the most user friendly, especially for someone with little experience.

I prefer Drupal over Joomla, much better structure IMHO. Easier to make mods if necessary.

Joomla is good but get enough juice to hold the integrity of the admin interface. Joomla customises easily with a few quick and dirty changes and many many cheap mods are available online.
Wordpress comes along but if you want o manage seirous text, control nuke is good too. I like the Google function which got me some tasty alexa rankings.