It's a big decision! We didn't know if we were having a boy or a girl, and whilst we had just one girls name, we had three boys names picked out. We had a favourite, and we did end up going with that one when DS was born.
However I did want to let you know that for the first few days after DS was born, it just felt so wrong calling him by his name. I was worried that we had made the wrong decision. I mentioned it to DH and he said he felt the same way, but his take on it was that it felt weird because we'd called DS by a combination of the boy and girl name before he was born (think 'Brangelina' but obviously not that!) and it was just taking us some time to get used to his name. So don't stress if you feel like that as well.
BTW, I love my DS's name, it's perfect for him.