I would recommend that you only add three units. That's the maximum stated by Google and anything over that just looks crazy in my opinion. No-one enjoys a website overly cluttered with advertisements. If you're building an authority site, defiantly don't clutter the site, as you're trying to attract visitors to come back.
Is the simple and 3 unit ads and approximately 2 or 3 link units and using one search bar from google adsense account. And set the good placement of the ads. when you achieve the right goal.