Open Patcher, make three instances of Maximus, route the Patcher input to each instance of Maximus, open the "Editor" tab and solo out each respective band in each respective instance of Maximus, done.
Either bounce out the section to audio or create three different instances of the instrument(not multi timbral) and copy the midi to all three. one with a low pass at 150-200 this will give you the lows, or you could take them out all together if you just want mid range, the next track has a hi pass and a low pass. put the hi pass at 150 or wherever the first tracks low pass cuts, then a low pass at around 2500 or so.add tonnes of modulation and effects to this track like DISTORTION and OVERDRIVE etc.... The third track put only a hi pass on wherever the previous low pass cuts, around 2500. this should give you a starting point. hope this helps
In ableton you can drop an EQ on the track and group it to itself, then duplicate the chain two times. . . . . .Now you have 3 parallel eq's Set them how you wish (low, mid high) then just chuck the fx you need, into each chain its needed. That helps with cpu usage.
If your not using Ableton, just do what Phobic said. Just make sure you bounce your tracks frequently to conserve cpu.
If you want to save on cpu try arranging the bass in its own project. then bounce it to audio and drag it into the track your working on or, pop it in a sampler and trigger the bass. add more fx if you want and bounce it down again to save on cpu.rinse repeat.also, not sure if you can freeze tracks in FL but that helps as well for cpu.
for FL Studio, the best option, IMO, is to use the Patcher. I normally work with two projects separately. I do the bass lines on the main project, without any resampling/effects to it. Just the raw synth sound. When I'm satisfied with how it sounds with the other elements on the track, I export it as wav, then load it unto my second project, so I can resample, split frequencies, and all that stuff. When it's done, I export again as wav, and load into the original project.