I bought the Kenwood 9990 for my 997 TT. I think my situation is a little different. I bought a Nav TV trim ring and MOST adapter box. I'm going to use the factory amp for the center and rear channels and my own amp for the front doors and sub. The front door speakers will be upgraded and be matched to an upgraded center channel speaker as well.

We have the 9990 installed and playing entirely with the factory amp for now as phase 1. The only outstanding issue is where to put the Kenwood microphone. It's temporarily in the pocket under the A/C controls but I'd like to find something that is higher in the car and not in the way as I often put my wallet in that pocket. Side note: the Nav TV integration box also incorporates volume, track and source for steering wheel controls. The phone button will act as play/pause if playing a CD or iTunes. It does nothing otherwise.

My installer followed the lead from this board and put the Sirius and GPS antennas under the windshield. Very slick.

In terms of the microphone, what has worked well for others?

 

I mounted mine right behind the steering wheel and it works great. I have an older kenwood excellon nav unit with bluetooth phone, and have not had many issues when using the mic.

I can take a picture, but it is attached with double sided tape right behind the steering wheel and in front of the gauge cluster. You barely even notice it is there most of the time.