We spent a while looking for a source for a good, inexpensive four channel ignition module. Finally we dropped the search and just made our own:
http://www.diyautotune.com/catalog/quadspark-four-channel-ignition-module-p-481.html
This should make things easier for anyone using the MS3X with coils that don't have built in ignition modules, and it can be used with non-MegaSquirt products as well. They're priced at $89 each and have a one year warranty.
