As Jazzyvee indicated, the missing link here is the power amp. Your current setup has all of these components (preamp, power amp, speakers) built into one box. Convenient, but with nowhere near the flexibility or tonal possibilities of a separate preamp and the power of a stand-alone power amp.
When it comes to power amps nowadays you can get a lot of power for the price (and easily run more than a single cab). What your looking for is adequate headroom for the contexts in which you play (e.g. a metal band in large venues vs. a folk/bluegrass group with miked acoustic instruments in small clubs). The better power amps also offer the option of stereo capabilities for those of us with series basses where you can run the neck PU through one channel to a separate cab and the bridge PU through a second channel to a different cab. People here use Crown, Yamaha, QSC, and a variety of other power amps a good deal of which have stereo/ two channel capabilities.
The other thing to think about is whether you’re going to be lugging that amp, preamp, and cabs all over the place or it’s going to sit in a studio. The new power amps can be serious light in weight as in 3-5 lbs versus 30 lbs. However when you add it all up a high quality combo rig is sometimes the way to go.
Of course, then there is the ultimate in tone shaping equipment, the Alembic SF2 that includes two filters with incredible range. But that’s a whole different story.