Very common names in the South end. Both St. Hyacinth and St. Stan's will have a load of information on them (though St Stan's is a bear to get research out of). Classmates.com would be a great place to find many members of the family, as most went to St. Stan's, All Saints and Central.
You'll also find Leppke in a lot of records as Lupcke. It was a spelling change made about 100 years ago.
Most also came over pre-Ellis Island. So once you work your way back to the 1800s, the passenger records will be online at www.castlegarden.org.