@HGSynth, marvelous response. Thank you for you insights. Shopping around for the rack, but focused on the rackbrute 6u. I've not seen anything but the 6u rackbrute available (I had originally thought that the 3u version would do), so I'm not anticipating a shortage of HP being available. I hadn't expected to ponder beyond a bit of modulation and some effects (lacking any on the mb 2s).
Minibrute 2s. I'd like to use the sequencer on the 2s for most of the sequencing and clock -- which also goes out to (or comes in from -- not sure which I prefer) an erica synths lxr-02 for drums, and do some processing, futzing, modulating of the bass lines on the rack.
I've added some randomness to the modules, yes. As I think more about sound, it seems that one of the true strengths of adding modular is getting a bit farther from the norms of integrated or even semi-modular synths.
I will read up on the modules you've hilighted above. Thank you again for your comments.