I'm assuming you're aware of Campaign Cartographer 3+ and Fractal Mapper 8 (with 64-bit FM9 in development), and that neither fllls your bill. In that case, you probably want MapForge (http://www.mapforge-software.com/), the successor to Dundjinni. It's a new program developed by Heruca, who was one of the top contributors in the good ol' days to the Dundjinni forum.