The only way to persist the data from RadSpreadsheet is, as you said, to save it as a binary stream. If you want to bind to different tables in the database, you may try using our RadGridView. For the time being RadSpreadsheet does not support external data-sources which you can bind to. In the future we would definitely consider adding this functionality, but we do not have a specific time frame which we can commit to.
All the best,
the Telerik team