I haven't watched Iron Man 1 in a while. It has some strong LFE in some scenes well below 25hz IIRC. At very loud volumes with the M80's set to large the LFE might be too much for the M80's at the volumes you are listening to. Without a more specific description, those noises could be also caused by the amplifier clipping during those dynamic peaks in the movie. The LFE content in Iron Man 1 can be taxing even with subwoofers, possibly causing "flapping", "rattling" and "farting" sounds. There is plenty of dynamic range in the Blu-ray soundtrack which might require power reserves in specific h/t applications and listening requirements.
