[Hydrocket]

Ok...we used a Pioneer DEH-710BT when my wife was a community nurse. The car was essentially her office, so call quality was important. The mic that comes with the unit can either be mounted on the visor, the mirror or in the A pillar as we did. It comes with a remote control too, which is pretty convenient. The calls play through the stereo speakers, so sound is as loud or quiet as you want. There was NEVER a complaint about sound quality on either end. The only down about the unit (mind you there are newer versions of this one) was that only one phone could be connected to the head unit at any given time. Excellent unit. Cost was $309 installed and out the door. Pics below.

Another option for you to try, and what she uses now is a top shelf ear piece with noise cancelling technology. She then got a custom ear mold for it. The sound is amazing. Even with the window DOWN, I can't hear any wind and sound quality is truly exceptional. I have no idea how they do it, but this earpiece is small, does voice dials/voice answer and sound clarity is exceptional. The one she used was a Jawbone ICON..she then had her earpiece custom made here: Jawbone Bluetooth Custom Molded Earpiece from AverySound.com

If you have further questions, please ask.