You will need to synchronise the data across. I believe Sage uses their own proprietary database. I use some open source software called TalenD, to create interfaces between databases. Perhaps, if there is a jdbc driver available for sage, you may be able to create a interface between the two systems.

You could export from Sage first and then run the interface on the exported files, if you want one way from Sage as well?

Sorry I could not be any more help.