Get the micro-versions of the Mutable stuff and buy a Eurorack module capable of mixing your signals. Unless you like the kick sounds in the Plaits, you may want to go in a different direction. The Intellijel Morgasmatron dual filter is great for making some tasty electronic kicks. But you'll want an envelope generator and a VCA to go with it. As an alternative, the Noise Engineering Basimilus Iteritas Alter makes for a good stand alone kick module with no other external gear. You can also use it as an VCO when not needing it for a kick.
Oh, and the Expert Sleepers Disting just got a few compressor algorithms, great for compressing drum drum mixes... but again, you're going to want some way to sum them and feed them into the compressor.
You may find it better to keep the Neutron in its own case and use your expensive rack HP for more modules.