Is the second "really" really needed? No, it isn't. Does it add influence? Absolutely. Do you really need to use a person's name when the two of you are the only ones in the room? No, you don't. Does it add an extra meaning? Yes. Can this "extra" word be used for meaning or stress? Absolutely! It's like the difference between saying "Yeah, you can," and "Yes, YOU, standing right in front of me, I KNOW you can!"