I have read as much info here as I possible can and still can't decide which gps is the right choice for me. I currently have a Nuvi 550 that I have hated since day 2 or so. What bothers me most is 2 things. It refuses to obey the avoidances and it changes the custom route when it turns off then on after a break. I don't want to get a new unit if these things will continue. I have narrowed it down to the Montana 600 but am leaning toward a reconditioned Zumo 350. The 590 is out of the question. I do about 80% pavement, 20% dirt roads and virtually no trails. What would you recommend?