The Valvoline full synthetic that you can get at Autozone is some pretty good stuff. I've never had fade problems driving on or off the track. I used to use ATE Super Blue on the M3 but its temp ratings really aren't much higher than the Valvoline stuff that's readily available and almost half the price.
I would suggest using the cheaper stuff (valvoline) and flushing more often, definitely more than once a year to keep it at peak performance.
BTW, did you get the stereo to work?