I don't think an unusual name is a problem. Invented names, names that just effectively didn't exist when you were born, can be problematic - but Sylvester's a very old name so it's fine in that department. I know lots of people with unique, older, or simply uncommon names - not a big deal.
The main place I think you might run into trouble in the "outing" department are names that you see constantly on kids young enough to be your own kids. For instance, for us twenty-somethings, Kayden/Jayden/Brayden etc might be appealing (because we're subject to our generation's naming tastes) but probably aren't great choices because there's essentially no way we could have gotten them unless we picked them ourselves. Of course, in the event that you really really like a name like that, or if people question another older/foreign/unique name you choose, you could just say your parents named you something hideously embarrassing so you got a name change. That's not unheard-of.