hijack: anyone know if you can run the garmin topo maps on the DNX 6160?
Yes you can, although the functionality will vary by GPS and is often limited.
All Garmin-based units I have messed with (including those in found in Kenwood) will load and display Garmin-compatible Topo, trail, etc. maps either those made by Garmin or those available freely on the internet. However, you'll encounter a few caveats and limits in functionality which will vary by unit. I have used various Garmin eTrex hiking units, several Nuvi series units and the Kenwood DNX210EX and spent limited time with the DNX5120 and DNX6140.
1. More often than not, 3D View is useless for Topo maps (doesn't display land features or elevation) or does not display at all. Switch to Track Up or North Up views.
2. Some Garmin units will not reliably display multiple mapsets simultaneously. I'm not sure if this is due to performance (RAM/Graphics) or just limitations of the device's capabilities. For example, my eTrex Vista HCx unit will display a single mapset file (a gmapsupp.img file) containing data from multiple map sources and overlay them on top of each other. It's a little slow sometimes, but it works. I have a road, trail and 24k topo and 100k topo maps all showing simultaneously on that GPS.
My wife's Kenwood DNX210EX (essentially a Nuvi 350 or so bundled with a Kenwood stereo), has limited internal memory almost completely taken up by the City Navigator 2010 road maps. I had to put the extra topo and hiking maps on the SD card. You can switch between map sets in the menu system. It does allow you to select multiple mapsets simultaneously and it does display data from all maps selected.
However, if all you have is the unit's internal memory, you can either cram multiple mapsets into one gmapsupp.img file or you can download one set of maps, rename gmapsupp.img to gmapsup2.img and then download a new set of maps into a gmapsupp.img file again. This also works as a way to get more than one mapset img file onto an SD card like on a phone using Garmin Mobile software…
3. Most on-road Garmin units will not route using topo maps (turn by turn directions) nor will they import your Routes or Tracks from MapSource. This is true for most on-road units like the Nuvi series, save for those couple of Nuvis that have combo maps out of the box. You'll have to switch back to the road mapset for your voice guided navigation or leave multiple mapsets selected including your on-road maps. The topo/trail map info will be displayed, but the unit will use the road maps for guidance. This of course can cause problems if there are no roads, but you shouldn't rely on voice guidance on the trail, only to get you there!
4. Finally, I haven't seen a Garmin on-road unit that records tracks (breadcrumbs). Most will not let you follow downloaded routes made offline in MapSource or create new routes from POIs/WayPoints stored in the unit either.
5. Waypoints in MapSource will end up as "Favorites" under the "Where to? ->My Locations" menu on most on-road Garmins. Useful for marking camp sites, trail heads and significant points within a trail.
So, at a minimum, at least you'll be able to load your favorite Topo and Trail maps, view them, browse, search them and have your little vehicle icon follow along with you on the trail. I personally would love to have tracks or routes but I haven't found an on-road in-dash unit that offers this level of functionality.
Still I think the Garmin-based on-road units are the best in-dash units just because I can load whatever map data and waypoints I want to into them and there are loads of free Garmin-compatible trail maps available on the internet, usually for free. I prefer to plan my trips offline in MapSource on the big computer screen too.
But if you want the full meal deal, you won't find an in-dash model that fits the bill. You'll have to go with a hiking oriented model like the eTrex, Oregon, Dakota or GPSMAP series. Or you can get a crossover model like the Jeep Trail Guide (Garmin Quest 2) or a "multi-mode" Nuvi like the 500 or 550.