I use a program called Oziexplorer. Have been for over 20 years. A Brisbane guy wrote it. Does most brands. Older C-Map, Northstars and Raymarines excluded. You have to scan all the charts in yourself and digitise 3+ longs and lats. The green zone maps from North Qld are good for base maps. I've got a hold of a lot of Admirilty charts and the old Sunmap charts. Works great for me. I do use GPS Utility or GPS Babel if I have to convert the odd file to different non standard formats. If you want a free online Navionics there is always this one to look at on a computer screen or tablet for route planning or distances etc.
http://www.fishandboat.com.au/navionics