OK, so here's the deal. I bought the Navigation unit, amp and jumper harness (connects the amp to the nav unit) from oemvalue.com. The 2004 Camry unit is nice because it does not have the external CPU that the 2003 model has. All of North America is on one DVD that inserts into the head unit.
The install was super easy. Just remove old stereo. Duct tape the GPS antenna to the ceiling of the underneath area of the dash, just over where the head unit sits (it gets fine reception here). I installed the amp in the little secret stow compartment inside the glovebox (I had to cut a hole in the back of it to run the wire harness). Plug all the wires in and reassemble the dash. IT works well. The steering wheel remote buttons work perfectly as well.
There are 2 complaints:
1) The buttons are green colored. I called all around Santa Monica stereo repair places, and they say they can't change the bulb colors...I will continue to try to find someone who can...
2) The sound is good to the front speakers, but it doesn't put a proportional amount of good sound to the rear door speakers. I tied to use the fader, but they just don't get very loud at all...
I still have the non-jbl speakers installed, and hope to change them in the near future...Perhaps I will change the amp as well. I still have a lot of research to do...
As for as the nav system, so far it works great. It is great for scoping shortcuts thru LA side streets during traffic, and it hasn't led me down a dead end yet!
Well, good luck, and let me know if you have anymore questions...
Mark