I'm impressed you are thinking names already - DH & I haven't really discussed at all!!! But I guess we didn't decide until later with the other two either
It's weird how your tastes change with time - when pg with DD, I was pretty confident that if she was a boy, we would name him Isaac. Well, when picking names for DS, Isaac wasn't even a contender on our list of names!!
Our tastes have definitely changed over time, and you learn some things about names. For example, we liked Noah for our first, but now I am so sick of the first syllable (no) after shouting it for 7 years. Also, you can try to be different but it doesn't always work. Our son Zachariah always gets called Zachary, which REALLY bothers me.
We decided on a name early with our first, I just knew he was a boy. I don't think we ever had a girl name for him. With our second we had a girl name and then the ultrasound showed us he was a boy. It took us forever to choose his name, we almost left the hospital with him unnamed! I felt so bad about that, I think that is why I want to be ready. We don't share names with anyone until we introduce them to the baby (other than sharing here), so we have a while to keep the secret this time. Plus we could still change our minds.