When Bo$e speakers first came out there were very few high power amps.
Bo$e speakers need a lot of power, so Bose got into the amp business.
After looking a the Bose amp schematic I found that it has 85vdc rails for the output stage. In theory it could deliver almost 600w RMS into a 8 ohm load at least for a short period of time, one channel driven. Thus I'm fairly sure it could provide 400w both channels driven.