ESP D-4 Replace Pickups or Effects Pedal?

I recently purchased an ESP D-4 bass, and a GK Neo 212-2. I'm really happy with both of my purchases, but I'm just not quite getting the "classic rock" sound that I'm looking for. I don't have a lot of experience with this type of equipment. I've already scooped the mids, but I'm just wondering what the best way to get a more Rock-like sound out of my rig. Whether I have to replace a pickup, or look for a pedal. I'd appreciate any advice. Thanks!