as a companion for the beatstep maybe take a look on the yarns. it could utilize 1-4 of the beatsteps sequencers instead of just 1.
also the saying goes "you can never have enough vca's" and thats true ;o) you will need an vca for EVERY single parameter you want to control the depth of, so one can generally not have enough. mixers are just vca's without control voltage.
also look into attenuverters like triatt, 3xmia, spo etc. and think about where you could use one.