Question about Infused Chocolate

What's the best kind of chocolate to infuse with coconut oil? I'm afraid adding the oil will mess up with the consistency of the chocolate. I don't want it to be oily and soft. I want hard consistency, the kind of chocolate that makes noise when you break it. My fist idea was strong dark chocolate, 70%-85% cocoa, but I don't know how well it will mix with coconut oil. Any tips?