The 660 is not a great device to play music on when wired into the Spyder.
The GPS (660) as priority over all audio, so if your listening to the radio, xm, weather, iPod etc and a direction comes in it you will hear it.
When you're playing audio (music or books) via the GPS the Spyder can not tell the difference between that and a direction. It just sense audio and plays that, when it detects no audio like a low part in a song or between music track it will resume what ever was playing before radio, xm, weather, iPod etc
You are able to physically switch between radio, xm, weather, iPod etc but not the GPS, it always on.
The 660 on the spyder is a not a great option to play music the way its wired and designed to work.
some things to check,
On your spyder:
go to settings -> audio -> make sure your speakers are on. They should be as your hearing FM radio but double check.
Then go to headset and check you have it on mix, if you have it on mute or off and your testing the GPS voice with out the head set on you will not get the right results.
On the GPS:
From the main screen choose audio, make sure mute is off and volume is 100%, then go into mixer and set both master and navigation to 100%
Then back the main screen go into tool -> settings -> system
make sure the usage mode is motorcycle (audio is handled differently between car and motorcycle mount)
See if any of that helps
other than that I would run back to the dealer
harry