Dude if your seeing smoke there is a big problem & chances are that its not in the speakers & not from having too much power,my guess would be that there is a problem within the reciever & the speaker terminals on the reciever are passing voltage through them.
Try this,take the speaker grill off a working speaker then turn on the reciever at a very low volume all the while watching the woofer,if the woofer extends or pushes out your reciever is passing voltage to the speaker & will need to be serviced.