I think the wmd performance mixer might be difficult to get hold of now that they've closed...
& due to the large number of sound sources I'm not convinced the cosmix pro (only 6 channels iirc) will be big enough
I have a tesseract modular tex-mix - which is both expandable and reasonably priced... it also has vcas built in (on the mono channels) that could free up a lot of your vca channels for other purposes...
given my philosophy (see signature) I'd want more utilities & probably more modulation sources... the matrix mixer looks like a good addition towards this though - multing 5 modulation sources to this will give you up to 15 modulation outputs - something your other modules are screaming out for!!!
I'd spend some time researching different types of utility module and thinking about how they can add to your patching...
even without a maths, although personally I think everyone should have a maths, downloading and reading through the 'maths illustrated supplement' a few times, concentrating on the how, what and why of each patch, can massively add to your patching repertoire
"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