Hi and welcome on the forums,

There is no secret or sources for good quality olive oil for the health benefits, you don't need to buy any expensive bottle labeled with fancy words, some Olive oil producers I've added a message on their bottle, something like "Good for your hearth" but it doesn't means that their Oil is better than another on this point, you just need to buy an
Extra Virgin Olive Oil with an acidity less than 0.8% see the difference here:
http://www.olives101.com/2007/10/31/grades-huile-d-olive-olives-oil-grade/Then it's a matter of taste, budget, uses, you can use a DOP AOC (which guarantee the Origin of the products but nothing else).
I will just recommend you to avoid the cheapest EVOO ;o)
Good luck