First, I'd like to say good job to Arturia. I worked with lots of drum machines and Spark is one of the easiest & intuitive I never worked with.
Well, I read lots of topics how to export in multi midi channels, and unfortunately it seems to not be available yet. If yes, please let me know how to ;-)
I used to do it with Maschine (Native Instrument) & NEED IT also with Spark. Everything is describe in this video : http://www.youtube.com/watch?v=cbzaYkIqV28
So Arturia, we're many people who need to export in multi midi. Please think about it mates for a next update...