I have the 507 with the with flow thru valves on recent trip to CO it paid for itself as I developed a leak on one of my valve stems the nut had loosen up and it detected it before I ruined a new tire. As a side note all four of nuts had loosen up! I think it was do to additional weight of the flow thru valves, so I would check them before installing them. I never did before Since then I have not had any problems on the return trip home, I might also note that the ambient air temp was over a 100 degrees as we went across Kansas when this occurred. Just a FYI
I also have the Garmin Dezel 760 which works great but it always good to have a paper map! I also use it for my voyager wireless back up camera.