Have you taken a look at the frontends at the top of the forum? Also, have you looked at the sticky with the mac links in it? If so, which programs did you not like and which is closest to your ideal?
Many people use FrontRow for its simple interface, particularly when paired with a device such as a Powermate, which makes it easy to navigate without having to take your eyes off of the road.
There are few options for Mac GPS, (RouteBuddy and Roadnav) but you can run Windows GPS programs using Parallels.