I believe the old FTC rule applied only to stereo (two channel) and mono amplifiers, either separate or in a receiver. It did not apply to amp/speaker combinations, such as a subwoofer, or to automobile products. For several years the FTC has been considering a new standard for multi-channel amps/receivers and while I don't think it is official yet, many manufacturers follow it, or ignore it as they please. As I understand, the new multichannel standard was devised by (don't laugh) Sony, Panasonic, and Bose (haha), so don't be surprised to hear that it only requires full power into ONE channel! Which is why many receivers rated at 5 X 100 watts really only put out about 30 watts all channels driven into 8 ohms. So buyer beware.

Dsmith