Believe me, if you intend to mainly use this as a live gigging modular, you'll find that you'll probably want the expansion fader module for the WMD. The VC mixer on my Digisound has seen WAY more use than you'd suspect, because I use it to slot different signal paths in and out when live. With each path being a separate "instrument", this means I have at least four different, discrete "voices" present on the mixer, and I can slot those in and out as the set goes on. Sure, it looks like "too much" mixer right now, but wait until you implement it in an actual set. It'll get real busy, real quick.
Also, keep the Plaits. Farkas is spot-on there. It gives you everything from analog TO digital as far as sound palettes go. And while I can see the point about Marbles (it really is more of a "studio module"), you might consider keeping it as it's one of the more comprehensive random-source manipulators around. Now, my take on the Maths vs Quadrax thing is this: try having BOTH, especially with the Qx expander. By crosspatching the Quadrax/Qx with the Maths, the resulting modulation behavior should be VERY elaborate...something you could even use to "glue" a set together by having the strange mod activity affect all of your patches in a live set in some way. Sort of like some of what you hear on Orbital's "Brown Album", in the long set that runs from "Lush 3-1" through "Walk Now".