I have first hand expierence with all these pieces, minus the actual nav on the kenwood, and considered both the N2 and D1 (look out for the Z1 in 06')
and heres my take on them all
Kenwood = decent little deck/screen but the problem is that it is a double din so no drivers info,
Avic N2 = Personally dont like this peice very much as a deck, especially the screen (compared to the Pio 7600 piece) but Pioneer Nav is by far my favorite nav system out there i have personally used, but it will definatly block the two air vents/ hazard lights
Avic D1 (Z1) = quite possibly my favorite piece out there, i love the doubledin, love the navi, love pretty much everything about it, minus the fact i cant put it in my G6
so pretty much your either losing either your drivers info, or your vents/hazard lights,
PS if you go with the D1, rember that it wont play DVDs so youll need a standalone DVD player if thats what you want
and if you buy the N2 you have to solder a conncetion together to make the movie, and navi work while driving....