how are you sequencing v/oct? maybe something to address that - otherwise, a small utility mixer, a couple of attenuators (2hp) and a disting mk4 would be my votes to just plug the physical gap and (any) gaps in functionality
I'd be tempted to go with a smaller mixer - you've got relatively little to mix for audio
the best advice is to go for as little as possible
maybe just get stages, the filter, plaits and the quad vca to start with and add a disting - and a sequencer if you need it
play the hell out of them and learn as much as you can about each module - try using different disting algorithms to see what they do and think about why you might want them. or not as the case may be - if you find yourself using the same one constantly then buy a module for that mode and use disting for something else
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities