Okay don't know anything about the D3s, but what is the 15GB of memory on the nav capable of??

thanks for any feedback!!

That 15GB is referring to the 2 map DVD'S you get with the unit. Memory nav stores your route so you can remove the map disk in order to play a CD or DVD movie. I have used it on a 500+ mile trip to Houston from the coast of MS and it stored the whole route.