I think you can load Topo on a Nuvi and choose to enable that map like on other Garmin units. They are limited in their track, waypoint and routing capabilities compared to the trail units. What bike do you plan to ride and on what route (A,B,C), Viper05?
2011 KTM 990 Adventure R
2010 KTM 530 EXC
2009 KTM 950 Super Enduro Erzberg Edition