GMXT (GarminMobileXT) is a program mainly for phones (and PDAs), in Symbian & Windows Mobile versions. It's basemap is smaller than the ones in GPS units.. DEM stands for Digital Elevation Modelling i think and is what shows shading on the map when you zoom out. A non-DEM map doesn't have that, so scrolling is quicker. You can remove DEM from any basemap using GMapTool. The basemap from your 1250 will work with GMPC.