Static Price Drop

Hi All,

Hope someone can help me.

I am looking for a way to give my customers discount when they order 20 random / or the same products. I already saw the following module: Category Based Discount

What is the deal:
I have products which are all different but they all cost 8 euro.
Customers who buy 20 products or more get all the products for 5 euro. So a 3 euro discount.

So I want a static price drop per product. When somebody orders 20 or more different / or the same / or 10 the same and 10 different products. When or if the total is above 20 or more products every product is 5 euro.

Would the Category Based Discount module work that way? And if not how can i make this construction work?

thanks in advance.