I don't mind my MIM J pick-ups, but I'm looking to replace them. My amp has terrible hum, and when I unplug the bass or turn the controls down the hum goes away. I'm wondering if this is the pick-ups or the amp, it might be both. Oh, which should I get? Fender 60's CS, or Dimarzio pups? I'm looking for punch, or something. Heh. Is there any diffirence between the regular Dimarzio J and the Dimarzio "Ultra J"?