ok I think it's more about how you would use more modulation and utilities though
to be honest probably just utilities would do - expand the capabilities of the modulation you already have - go and take a look at the doepfer catalogue - look for anything that does not produce sound or process sound and read the manual - it's a page or less generally - think about how you might use that module in your rack - then work out which ones you are interested in and look for alternatives - work out which one you want to play with and get that
maybe I'd add either zadar or batumi but only a maybe... but only after I'd tried the above
"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