Yikes! That's scary when you think you are set on a name, then the other starts throwing out other names! I haven't seen Austin on the Top 100 list so I wouldn't think it's to popular, and you're absolutely right that once you pick something, you see it everywhere!
I don't even want to say where our name choices are at right now, it's not looking good at all! lol
OMG, something is in the water because I texted DH a question about the baby and when he saw Emeline in written form he questioned the spelling. So we went through about a week before he decided that he really liked the name still so he gave into my spelling. His name list was Emma, Lillian, and Olivia. I liked Emeline and he figured that was a good combo of Emma and Lillian and then Olivia for a middle. So all his names were used, he could at least compromise on the spelling. I was so stressed out that we were going to have to find another name.
With my first, we picked a name very quickly and that was that...we knew her name for months before she was born. So when we couldn't solidify a decision with my second, it made me CRAZY!!! However, I loved looking at him before finalizing his name in the end and now we aren't going to make a for sure decision until we meet this little guy either. Had we picked DS's name earlier, it likely wouldn't have been the one we picked in the end and his name is PERFECT for him!
Just trying to put a positive spin in your situation I can imagine that's really frustrating though.