There's an update in the works that will bring the 660 up to the 665 minus the XM obviously. I haven't heard anyone confirm the multitrack thing...
It's identical to the 660 Bonus, just has XM.
Here are some Zumo 665 screenshots that I have gathered from here and there. Same unit as the 660 but with XM radio and what seems to be the most...
Or you can get some custom molded ones that cut out the bad sounds at the same time. They stay put in your ear better from what I hear.
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