Were I filling out this system I would next go for an Intellijel Quadrax (or perhaps Quadra) and then a QuadVCA. At that point you'd still have all Intellijel modules which is visually (and sonically) pretty.
Maths is a function generator. Quadrax is also a function generator. They're different but serve roughly the same roles. Things like signal level balance are likely to be better between modules by the same manufacturer.