Number of posts according to category

Hi,
I’m toying with WP and trying to use it as a CMS in a simple website. Now my problem is that I want to have a different number of posts in each page of the various categories (sections) of my site.
For example one category lists the posts with an image heading. In this case I only need 3 posts per page. Another category has just posts with text and I find that 6 post per page would be more suitable.
Is that possible with a plugin or is there another way to accomplish it? I found the perpage plugin, but it is not what I’m looking for.

Thanks for your help.