Any suggestions on what GPS to buy? Off road only. I really would like to have a standalone GPS, not an app on my phone. Was looking at the Garmin Montana 610 but have saw mixed reviews. Looks like the 680 just has a camera added and the T models have the 100k maps installed. Looks like the 100k maps are not that great and would need to buy or download 24k maps. I'm a newbie to the GPS world so any info is good.