I've added all that content, it shouldn't lose ranking on the money pages.
Much would depend on how intensively the new content was being linked to by the original part of the site.
Be restrained about adding new links to your internal navigation until you're confident that the flow of Page Rank is strong enough to be spread among that many new pages.
Adding many new pages to a site is kind of like changing the ventilation within a mine shaft. If you open new vents you'll get fresh air flowing into new corners, but you need to plan carefully so you don't make the air flow too weak within existing channels. PR is like that ...