Who makes the factory Nav radio? And...

If you choose to get an aftermarket Nav such as the Kenwood will the XM adapter fit that or does it have to be ordered for the Kenwood specifically? Anyone here using a Kenwood Nav unit? Do you like it? Was looking at the ddx6019 with the add on GPS.
 
Thanks...

I have a Kenwood DDX-8019 with the Kenwood GPS in my 07 Tahoe. Works great and very easy to install.

I believe Denso makes the OEM Nav for GM.
http://www.globaldensoproducts.com/ic/car_nav.html
 
I've read a few people have been swapping the OEM Nav with Pioneer AVIC-Z2.
http://www.pioneerelectronics.com/pna/v3/pg/product/details/0,,2076_310069681_423070352,00.html

Which model of the Kenwood has GPS already built in. I couldn't tell even from going to their different advertisers. The DDX 8100 sounded like an in dash DVD player with GPS capability but I sure might have read that wrong. The DNX 7100 sounded like a GPS receiver but then never talked about any of it's GPS features in the spew talking about the problem.
 
Where does Kenwood hide their antenna and does it hide away well? Will the existing XM radio plug up to it? Are the plugs compatible with it especially the buttons on the steering wheel?
 
Thanks... Gary