I am looking at putting in a Zone 2 audio in my breezeway between my house and garage. I would like to get a volume switch that would also allow friends/family to plug, through bluetooth if possible, their phones in to play their own music as well. Right now my living room is running a Onkyo TX-NR515 which I was going to use the powered Zone 2 of to run the two Polk RC80i speakers.
I use BT in a couple of our rooms. First thing to consider is range. Since BT is only good for 20 - 30 feet, make sure the receiver is centrally located - otherwise you might have static or choppy sound if the person with the phone wanders too far away from the BT receiver.