Good head unit to upgrade a base Z with if I just want nav and camera?

Nillaz

That's not a bad unit at all. Kenwood's have a wealth of audio adjustments, and no one else has Garmin Nav.

Having said that personally I would trade off the volume knob in a second for a unit with a capacitive screen. They're simply superior in every way. If you're really set on the knob by all means go for the DNX692, but keep in mind that the Z has audio controls on the steering wheel if you're worried about goofing around with the screen while driving.

I used to swear by Kenwood cameras but I'm just not so thrilled with them anymore. Cheap cameras nowadays can produce a decent (i.e. "good enough") picture for a fraction of the price. I used to use surface mount cameras but with my last install I went with a taotronics license plate camera...admittedly these things certainly aren't for everybody. The color reproduction isn't going to win any awards but it's particularly good at night and the install was easy as pie.