Want to use Multiple Themes on a single domain. Should I use Multi Site?

Hi All,
I’ve been trying to figure out the best way to use multiple themes with a single WordPress install. Not thinking this was possible, I was going to use MultiSite.

However when I started doing some research I discovered this article: http://codex.wordpress.org/Before_You_Create_A_Network titled “Before You Create A Network” and this statement really caught me off guard:

For example, if all you want is for different collections of web pages to look very different, then you can probably achieve what you want in a single site by using a plugin to switch themes, templates, or stylesheets.

Does anyone know what plugin would help me achieve this? Or do I in-fact need to use Multisite?