lol, I usually do the exact opposite. Tilt my seat back, and raise it. (Don't have my ST yet, but I find this is what I do in most vehicles I drive).
If I remember correctly the speed controlled volume for the stereo is contained in the somewhere in the menu when you press the "sound" button on the dash. There are something like 8 different levels of adjustment for it. Nothing as fancy as you had mentioned, but it does help block out some road noise when traveling at high speeds.I haven't even read the manual yet but I hope I can find speed/rpm sensitive volume because I find myself adjusting the volume often and I would set it to turn down the volume when the rpm is enough to let the symposer speak.
Actually adding a derivative function to watch engine speed rate of change would be the way to do it, so you would have a speed curve to counter wind and road noise, an rpm function to counter/enhance engine noise and then dv/dt to let it speak as soon as you start accelerating.
I still have to check out helmet clearance and the head rest.
My first autocross is coming up soon so I want to have that figured out.