I have a K-mix and there are a couple of things I can tell ya:
You should definitely have a computer that is a bit newer than mine. I’m on a late 2011 MBP 2.2 GHz Intel Core i7 running yosemite, and I have issues with the audio. It will crackle out every 5-15 minutes and I have to restart it to fix it.
It works perfect when stand-alone (no usb) and I love having it with me wherever I go. It’s when I try to interface with it that I have the troubles.
I have communicated a whole bunch with KMI about it, and they assure me the crackle issues will go away if I update to Sierra, so I haven’t sold it yet because I plan to do that one of these days.
I think it is resolved in El Capitan as well, but it’s not very good with yosemite and my computer.
So right now my K-mix is only being used to run the midi expander so I can slave ableton to my OT (master)/ rytm (thru).
I can probably answer more questions if you’ve got 'em.