now that I have the Aux-input installed, I am thinking of putting in an active noise cancellation module. I would simply splice into the aux-input and adjust the gain/filter so the music is not lost. Maybe run a small microphone to the headrest or just low and close to the shifter to better capture the low rumbles.

this unit looks promising, though it was specifically designed to filter for voice:

http://www.bhinstrumentation.co.uk/html/neim1031.html

also check out:

http://www.audioscientific.com/Noise%20Can...ors%20Links.htm

any thoughts? any other suggestions? it seems fairly simple to do, at least for a test.