Nav directions/Pandora via Aux Input with phone calls via BT...

So I'm trying to figure out a cost effective setup for my Tacoma (1st Gen). I have a Motorola Droid and am trying to decide on what type of headunit to get. I would like a double din with Nav, but considering how much better Google Maps is, I'm thinking about getting a regular deck and connecting my phone to it. I'm trying to figure out if this will work...

If you get a headunit that only supports BT to talk, but has an Aux input, can you still pair your phone to the headunit for the phone and have the Nav and Pandora play over your car speakers via Aux input? If so, will the music/nav mute when a phone call comes in? OR will music mute when Nav has directions to tell you??

I'm pretty sure that if you have a headunit that can stream bluetooth audio, you can connect your phone to it and it should work with all three (BT to talk, pandora, and nav) with all the proper muting to take place when something comes in to disrupt. Is this true?