When you say oomph, do you mean something tonally that it lacks or is it just a lower output? If it's a tone thing, well, you've already got a preamp in your amp. See if you can get the kind of tone you're looking for with the existing pickups and the EQ and gain stage of your amplifier. If you still think it's lacking, you may need to replace your pickups to get what you need. You don't need to get actives, there are plenty of passive pickups to suit all kinds of tonal requirements these days. The choice has never been greater but you still need to be able to define what it is you want and then hunt down the pickups which will do it for you. For me, the pickups are the most important part of the instrument. Get them right and you should be able to run with no EQ and be really close to your desired tone. If I have a bass I need to tweak the bejesus out of to get the sound I want, then either the pickups get replaced or the bass gets eased on out the door.