Badass Bass II Bridge
 

If your looking for some fantastic sustain and great deep attack from the low end, you should really try putting one of these on a beater or some other bass your not really attached too, if for some reason you dont like it. It's really dense though, and if you've got a bad back maybe not the best choice. It's really easy to install, and gives some real clarity to your basslines, so I'd really try one out. I've got one on my 1990 squier, and it sounds even better then before.