It’s not preppy sounding but [name_f]Audra[/name_f] is a cool alternative to [name_f]Audrey[/name_f].
Maybe my thoughts on preppy and sophisticated differ from yours, but classic names are what come to mind for me. From your list I like [name_f]Audrey[/name_f] and [name_u]Meredith[/name_u]. Other names not in the top 100 that I think fit the bill: [name_f]Catherine[/name_f]/[name_f]Katherine[/name_f], [name_f]Josephine[/name_f], [name_f]Alexandra[/name_f], [name_f]Margaret[/name_f], [name_f]Cecilia[/name_f], [name_f]Genevieve[/name_f]… polished names with nice nickname options.