I think that people like the Sadowsky because it doesn't change the tonal characterstics of Fender basses, whereas a lot of the units people have mentioned do and impart their own characteristics more than the bass itself. I think people like the classic Fender sounds they have heard on records, but usually you can't quite get that sound with just the bass into most amps - adding the Sadowsky pre-amp gets the sound that classic Fender lovers want without making the sound more "modern" or somehow different. Mid-controls are irrelevant in this situation, as this would alter the characteristic Fender sound beyond recognition, which is not the idea.