you have quite a reasonable amount of modulation in the case already - I would head for utilities - a matrix mixer for mixing modulation sources together in different ratios seems like a good idea to me! - or even better the 4ms VCAM - voltage controlled matrix mixer with mutes or the instruo lion

"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