I have looked at the electrical on the 2008 and 2009 bikes. The audio output from the GPS harness is mono to the radio. I do not have the electrical for the 2010 radio.
The Garmin 2820 did not output the XM audio through this connection. You had to plug in to the external 3.5mm jack for this audio.
Apparently the Zumo 665 will output the stereo audio through Bluetooth or through the motorcycle harness in stereo. I have asked Garmin several questions on this, and that is what they are telling me.
There is a handy little 3.5mm to bluetooth adapter available from
http://www.imcmoto.com/called the D1000. It works while being charged.
http://imcmoto.com/products/bluetooth-adapters/wirevo-d1000.html
I choose to use the Victory mount for my bike and their harness. But there are other ways to go.
http://www.ram-mounts.com/.. Cables from
http://www.powerlet.com/, and you can buy the victory connector and make your own harness. Let me know if you need that info.
I am trying to find a way to take the output of the 2008 and 2009 radios and connect it to the D1000 bluetooth device. This way I can send the GPS and the Victory radio and all sources up to my Interphone F4 headset. This means I do not need my iPod to bluetooth in I can leave it on the Victory radio with all its functions coming up bluetooth.
If I could do this all over I would purchase the Garmin Zumo 665. Connect my cell and XM through it to my headset. Have my ipod, AM/FM radio, and weather channels come off the bike through the D1000.
If anyone has the Vision 2010 Service Manual and electrical in a PDF that I can get from you I would appreciate having a look at this.
Cheers..