GPS receiver with detailed US roadmap

I am considering to purchase this GPS reciever, but i am in need of detailed topographical maps of the united states and would like a more detailed US roadmap. i would like to know how i can aquire these, and how much they will cost me.

Hi

You can purchase a map model of any GPS and obtain the maps as needed under accessories.

Try the Magellan eXplorist XL recreational GPS receiver 98081201 and a Magellan (Thales) 980611-09 GPS Software - 3D Topo MapSend for USA - 98061109.

You can also do the same for a Garmin Mapping Handheld GPSMAP 60CSx Waterproof Navigational Device 010-00422-00, or Bushnell ONIX 200 GPS Handheld Navigation w/ Satellite Imagery Onix200 362000 and get the maps from thier websites.