I have rently ordered the 'realist' pick up, and have decided to get a pre amp. i have never used a preamp before. I hear good things about K&K, and saw that they can be fitted to the tailpiece (bob gollihur), which looks nifty. But do different preamps have different sounds? I play a nice old german carved bass, and use a swr workingmans 15"amp. Any advice please?