Matt, I suppose it's too late now, but I had completely forgotten about a product that may have worked well for you. We've brought it up in at least one other thread a long time ago, the Parrot BT hands-free/music kit.

Their MKi9000 is a box you wire into your car's stereo system in behind the dash. This can be accomplished in a few different ways, including through aux connectors, splicing, adapters, etc. Depending on the model of car/head unit you have. Then it also comes with an included remote you can mount to your steering wheel or dash. There's also a mic you can mount in various places in the car.

The hidden unit does all the BT stuff with your phone, including A2DP and AVRCP. The remote talks to that unit using proprietary RF as far as I know.

The net result is integration of your BT phone with your factory audio system. It also allows voice dialing because the unit can load the contacts from your phone using another BT profile. You can also answer and hand up on calls in addition to the regular music/audio controls from the remote.

If you have steering wheel controls, you can also add another adapter to patch those into the Parrot unit.