Beating panda with quality content - Index page only or whole site?

I just proceeded to adding 8-10 lines paragraphs of highly descriptive and quality content to about 25 inner pages on my website.

Will this help my index page (raw .com url) rank better in the search engines or does the content has to be on the index page?

Quality content is for your readers, not Google. Google can only use visitor behaviors as indicators of quality, but it does not know what quality it is-- only unique content. It will help your pages rank better if your bounce rate is lower, visitors spend more time on the page, interact socially with your site, and the content is unique.