I haven't had much luck on the "stupid" question I asked either but it is similar. According to everything I have read all of the speakers are used when playing the guitar. The main speaker giving off the "dry" guitar tone, and the smaller speakers giving the "wet" or effects signal. When playing music trough the system all speakers are also active as well.
What I was trying to determine is if there was a full signal direct out that could be sent to the mixer at a live show, and if not if there were any special mic'ing concerns to get the full sound of the amp as I am not sure just putting a mic on the main guitar speaker is going to be sufficient to capture the fully processed guitar signal. This could be a problem. If it can only be effectively used as a stand along amp then its only going to be good for rehearsals and small club gigs where you are not micing up the band. I really like the idea of this amp, but do not want to spend $499 on a practice amp that I cannot easily use at larger live shows.