How much should I sell my car for?

I have a silver 2000 Subaru Impreza 2.5 rs with 135k miles on it. Well kept, runs smooth, new tune up, needs a Freon boost for a/c, NOTHING wrong with the car, automatic, AWD , power everything, 4 door, sun roof, very fast even though its stock, spoiler, hood scoop, 4 cylinder, performance vehicle. All around great vehicle.