shh!
I'd want more mixing capabilities - mostly for submixes, but also for modulation (matrix mixer) - also possibly some way of placing things in stereo (panning mixer) - possibly sacrifice one of the modulation sources - quad cascading vcas are also really useful - veils for example
possibly replace the dual fx with a couple of fx aids
how are you intending to sequence?
it may be an idea to look at a trigger sequencer - metron appears to be good - also eloquencer and erica synths do one - some of these will also sequence v/oct and/or modulation - which is useful
what to buy first - a way to sequence - kick, snare, hats - mixer (or quad cascading vca) - an effect - a modulation source
"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