Sylvia is lovely. It's a beautiful name, meaning, classic, features in literature etc. Yes it was also popular 80+ years ago, there are some old ladies named Sylvia, so what? Some posters need to get over their prejudices about names and stop being quite so sheep like about fashions in names.
'Ooh no, I know grannies called Sylvia, uurgh! - Sylvie though, that's lovely'. What an original thought! You only think that because Sylvie is the French version of Sylvie and therefore less familiar to you, you probably don't know older women named Sylvie.
Meanwhile in France they think Sylvie is a middle aged name apparently. Again, so what?
So yes Sylvia, although Celia is also nice, but I prefer Cecilia.