AISynthesis do a matrix mixer in 10hp - I would go for that rather than the latest, greatest - unless you've got a pin fetish!!
In a small case I would rather have logic and rectification and sample and hold in 4hp - instead of 3 sample and hold!!
again adsr? do you need it? if so go smaller!!
do you really need the output module? if for headphones I'd get the 2hp or alm busy circuits... otherwise I'd just use 1/8"->1/4" cables straight out of mixer

"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