I recently returned my Kenwood KVT-512 and KNA-G510 for the Avic F90BT. Why??? Because for the same price, there is no external unit, the Avic has BT and and this thing can be modified up the butt...
It has more features than the KVT-512, so I decided to go with that. I will have pictures posted of how I did the remap of the pinout to allow DVD, poi selection, and directions while driving.
I did not connect the VSS wire and I might be adding an amp to power a small subwoofer box that goes either under the seat or under the dash. I have the subwoofer I want to use, just construction is being a pain, plus the time it takes to construct the box.