Jerry,
The F100 ia just a newer version of the FA1. The OS and all the sounds are the same, however the styles are different, with an emphasis on more classic organ styles. The cabinet looks a bit more like a small theater organ. The major difference is the sound system. While the FA1 is wonderful to hear the F-100 is thrilling to hear. BEWARE all loose objects tend to fall to the floor when the full power of the
F-100 is expressed.
Frank