Transformation

Yes, you could put an EMG-P or several others in it. If your tone control doesn't work right, you might just want to replace it. It's not too hard. Also, there are plenty of passive pickups that will kick up your sound quite a bit, and probably be louder than the stocker. Depends on what you're looking for.

 

The Seymour Duncan Quarter Pound (SPB-3) and Hot for P-Bass (SPB-2) are both pretty loud. I REALLY like the SPB-2, but the Quarter Pound is pretty popular, too. If you just want volume, however, an inexpensive option is the Rolls Red Square, which is supposed to be a Sonic Maximizer/exciter type thing, but will function as a preamp with active tone controls.

You can get the pickups listed above for about $60, or maybe less if you shop really hard (you're in the US, right? I forgot to check), but that's just the pickup, no wiring, labor, etc. I think you can get a Red Square for somewhere in that price range, too.