Hello all,
I thought that you may be interested in a DIY drum brain I am building. I call it Drum Master, you can read about it at http://drummaster.thecave.homeunix.org/ . It uses a computer as the mixer / sythn, and works across platforms (Mac / Linux / Windows). It’s a bit complicated, and requires soldering experience, but has been a very fun project for me. 
The designs / board layout / schematics are all released under a creative commons license, as described on the site.
Enjoy!
–Wyatt
