Is there a dedicated dash GPS that can use Google Maps?

You could use a TomTom GO6200 Wifi which has a 6" screen and uses the same traffic as Google. In fact, only TomTom and Google have live traffic. Another benefit is you can make commands vocally and use your contacts from phone via BlueTooth to send routes to it. I use the GO5200 as the 5" screen is fine. Also my car has its own Nav in it on a 8" screen, but I use Android Map GOMobile on it as the GM car nav routing is cr*p. So you really have two suggestions