micky wrote:
I'm thinking of installing a Gromaudio device that, if your car radio
has a CD changer input jack, allows for USB input, AUX input from a
cellphone, and for another $50 Bluetooth use of the cellphone through
the car speakers and an add-on microphone (in addition to the first
$150).

The most important feature for me is the USB input.

Forget the input jack and use FM wireless. Search Ebay.

IMO, bluetooth phone in a vehicle does not work very well.
The outgoing sounds are muffled, distorted, and hard to understand.
However, if you want to send music from your ipod to the vehicle
audio it works well enough.