Afriad not guys.
I have a Parrot CK3300 kit. When you play music it just comes out the speaker on the phone, same as the guidence voice in TomTom..........
....However on random times, like really random software faults with either the phone of the bluetooth headset, it will send the music/tomtom voice to the car kit.
Also on this forum i remember reading the same question but for the C500. There was some kind of Reg hack for the PPC hardware to allow it but not for WM.
There you go, oh and if you could it would drain the battery so quickly.
Running media player > bluetooth all transmitting all the time
and as far as i know Bluetooth has a SLOW transfer rate. So therefor the quality would be well... ...pish!