Where they really missed the boat is not having an audio-in port.
They tried to make the 550 and now the 660 a central-point audio system, on top of the Nav, by allowing bluetooth phone connection and it's on-board "entertainment" MP3 player and SAT Radio capability. But it sucks completely because the bluetooth is mono, but could have been stereo compliant because A2DP was available at the time.
The 660 is dumb because now, they've cut the SAT radio option, so it's left with it's MP3 player and phone connection, and yippee, it finally has stereo bluetooth. But the thing they should realize is most people have their own, more capable MP3 players, and SAT radios.
If they wanted to design a true audio system, they should have left it with the phone connection and provided an audio-in port for whatever else people want to jack through it.
Weird, because they make audio panels for aircraft, so one would think they'd know better.