He's referring to the Beltronics STiR controller seen in one of the pics. I would figure out if it's just the controller or the full unit installed. The full unit was $1,200 before it was discontinued.
Same as this one.
I agree the car's interior isn't spotless but an interior detail should help. The leather looks fine for a used car. I'm not sure where the OP is located since the dealership is in Tampa, FL. If you're not tied down to a specific color and in FL, I would make an offer on this one instead maybe without all the mods to see if it fits within your budget. Yes it's priced higher but it's a newer model year so you get the LCI tail lights plus an extra year of factory warranty.
http://f80.bimmerpost.com/forums/sho....php?t=1465824