MATHS is fine...it's probably the best bang-for-buck complex modulation source out there. The only concern I have here is about that MS-20, since it uses a different CV scaling and inverted gate/triggers, and usually that means a standard-changer module needs to be in the system...but only if you're needing to fully link this cab and the MS-20. But sending voltage curves from the MATHS directly into the '20s patch panel...that won't need that. Plus, there are a few 'creative' ways to fudge the MS-20 into some neat behavior by using its external processor section to do a little 'mistranslation' of incoming signals. Try feeding it some electronic percussion signals, for example, and then spreading the results out to both the '20 and the modular. Depending on how much early Aphex Twin you've heard, the results might seem...familiar.