Re: SVC Auto volume???
Quite so, Bose have a lot of experience with feedback circuitry (for instance with their noise-cancelling headphones) and the microphone thing with their car set-up doesn't surprise me.
But it doesn't need to be that complicated, my old Blaupunkt unit just took a speed signal off the car speedo and then there were 3 different levels of speed-related attenuation selectable in the menu, high, medium and low. One of them would suit your car, depending on the road/engine noise in the cabin. Surprisingly effective, and even if it wasn't perfect, a lot better than having no adjustment at all. I never had to touch my volume knob once it was set up on the right one. It was a lot more subtle than 'increments' too, the attenuation would be smoothly variable with engine speed, almost undetectable, as the cabin noise varied the radio level didn't seem to change in relation to it at all...if that makes sense!