Advice regarding how to control appearance for different sections of a blog site--use subthemes?

Hi All,

I'm working on a custom theme that will be used for a blog site. This theme will have 5 subtle variations:

1. Homepage, which will say "from the {customer name} blogs" across the top
2. Four separate blog "sections", each of which will have:
   
   1. A different header background image, and color scheme for the post titles/post footer links
   2. The name of the section at the top of the page (E.g., "Teaching Tips" for the Teaching Tips section)
   3. An icon to the left of the section name (e.g., "Teaching Tips" will have a book icon next to it)
   4. The navbar at the top of the page will have the current section in bold, and with an icon above it signifying it is the current section

I am not sure what the appropriate way to handle this in Drupal is, and would like some feedback.

First off, I'm thinking that any given post will be tagged with an appropriate taxonomy term that represents what section they are in.

Then, on the individual pages, depending on what taxonomy term is selected, the theme will need to be slightly different.

Should I create 5 different subthemes based off a parent theme, and use one for each section and the homepage? Or should I simply have one theme and check at display time what the current taxonomy term is (or if we're on the homepage) and modify the theme output accordingly?

Thanks for any suggestions. I'd like to do this "right" and not cause myself more headache down the road! I am still new to Drupal theming.

-Josh