I don't know if you're Sitex is on that list: SVS-460 4, SVS-560 5, SVS-750, SVS-760 7 but if the answer is yes, the Navionics+ is compatible and you will get SonarCharts: 1foot contour to 80ft.,and 3ft contour to 180ft if my memory is right.
SonarChartsâ„¢ is an HD bathymetry map featuring extraordinary bottom contour detail, great for increasing awareness of shallow waters and for locating fishing areas at any depth level.
You also get Community edit and free up-date for a year.
http://www.navionics.com/en/navionics-plus