I think you will be OK. While the amplifiers may have short peaks at high current during the loud segments of movies, most of the time you will be listening with a couple of watts or so. 40 watts driving my speakers in my room would be very, very loud indeed. I doubt seriously that you will destroy any speakers. If you are worried about it, then you can consider fusing them.
Most of the amplifier power is overhead. It isn't used all the time in a class AB amp like you're probably talking about. It is there to handle high current peaks like explosions in movie soundtracks. Most of the time you will be using a small fraction of the available power.
Be sure you balance the speakers properly with each other for output. You wouldn't want your surrounds balanced louder than your mains, as an example. Your receiver or preamp will have a routine for channel balancing. You should do this with a sound pressure meter if you can or by ear if you can't.
