Looks like with a bit of work and/or money you can cram two single-DIN stereos in there.

I have a Garmin StreetPilot III. I have used Kenwood (OEM Lexus) and Alpine's (OEM Acura) in-dash touchscreen NAV units. The Kenwood was the better one, and the Alpine was just horrible in my opinion. The Garmin is a usually a pleasure to use, is portable, and it costs nothing to install. It also interfaces with your computer for route planning and such. Like the empeg, you can also take it out of your car so it doesn't get stolen. The new Garmin 2610 (which I got for my father) also has a touchscreen and IR remote. That's the way I would go if you care... an empeg sled in every car and a Garmin mount on every dash!