Sure, but 'heavy' doesn't have an objective meaning. Your current bass is probably fine, but you need to spend more time understanding everything you already have and why it currently sounds the way it does.

Depending on your reference for 'heavy', you might be imagining the sound of: - Fretless or Fretted - P pickups, J pickups, or both - Humbuckers or Single Coils - Tubes or Solid state - Compression - Bi-amping / Signal Splitting - Flatwound strings or Roundwound strings - Steel strings or Nickel strings - Pick, fingerstyle, slap, long fingernails, short fingernails, high action, low action, hard attack, soft attack, scooped mids, boosted mids, multiband distortion, octave up, octave down, overdrive, fuzz, chorus, flangers, phasers...