Yea the mS-20 is solid especially the pure synth version:
http://www.korg.com/us/products/dj/ms_20mkit/
Pair that with my Elektron Analog 4 and Octatrack and the other modular gear and have wacky industrial dirt techno insanity!
I already have a Volca Beats that as you suggested can feed in percussion to the MS-20. I don't want the keyboard version but having trouble finding this pure synth kit. Maybe it is a new product release from Korg?
Anyways been learning my new Elektron gear the A4 and Octatrack as well as 0-coast and they integrate nicely together.
I ran an experiment this weekend: control the 0-coast with the A4, layer FX on top of that from the A4, sample that into the Octatrack and then add slices and resample with dirt from the Octatrack like dark reverb for some madness.
Since the Octatrack has room for 4 devices to connect, that would let me hook up the MS-20 and sample/mangle that.
Ideally I would need an additional sampler/mixer to add for the modular gear.