I have a Yamaha BBN5, which is a middle-of-the-line 5-string bass with passive J-style pickups. It's a good bass for the money, but I don't like the sound very much; it's too smooth. What would be the best pickups to create a fat growl on the bottom end? I don't expect it to sound exactly like a Music Man Stingray 5 or whatever, but I think new pickups would really help. Any suggestions?