You could go with the proper in dash satnavs, or save yourself a small fortune and have a stand alone system, they are really neat these days and work well in the smarties.
I have the Garmin Nuvi 1300t, the t is for free traffic alert updates for life, and here in Britain it comes in handy.
You can also get free silly voices from the garmin website, I particularly like Squirrely, he's nuts! or there is a link to paid for voices, I have Ozzy Ozbourne,Arnie, and Yoda!
You can also transfer it between vehicles.