Why not just put a retina iPad mini in the centre console, and use Siri for voice commands. An iPhone could also be used as a wireless hotspot while driving for the iPad.
Not to mention an iPad Mini would be a heck of a lot cheaper. As long as you already have an amp with USB connectivity, that setup could work fine.
I'm not sure why there's an obsession with getting WiFi connectivity to work. Wouldn't Bluetooth accomplish the same thing? I have a Bluetooth stereo in my current car and it works fine with my iPhone (though its interface sucks).