Hi Jaysus,

and welcome! You got most of the basics covered - you should get a VCO as the voice of your system, though. The range of choices here is huge (starting with the question of analog/digital...). Intellijel's dixie might be somethingm, or the Tiptop Z3000, or the WMD spectrum, Doepfer has a selection of VCOs as well ...
You might throw out the Performance mixer to clear rackspace for that.
Also, you should get a dedicated VCA. I can really recommend Intellijel's uVCA. It's not too expensive and does not take up too much space.
Finally, I am not sure if you need the multiple really.
Hope that helps you on a bit.
Best,
phineas