A few questions on bluetooth, if you can help?

[torrenter]

I was thinking of buying a new bluetooth capable mp3 player and bluetooth headphones/headset, but it led me to a few questions on the technology.

1. Does listening through bluetooth headset reduce the quality (e.g mono, compared to stereo)?

2. Does bluetooth allow different branded mp3 players and headsets to be interlinked? I was thinking of mainly the Samsung YP-T10JCB working with Sony's DR-BT21G headset, or Sony's NWZ-A828K working with Samsung's YA-BH270B headset. These mp3 players are the one's I'm most interested in.

3. Can you have a separate mp3 player and mobile linked to the same headset, so that you can listen to music, take a call, then carry on listening to music, seamlessly?