Marantz MM-9000 amp driving the front three. Receiver driving the surrounds. The room was 15 feet wide and 22 feet long with a 12 foot vaulted ceiling. There were no acoustic treatments at all, though the room sounded reasonably good. The volume at which I felt the sound was becoming compressed was high enough bad for your hearing. I never heard any clipping from the amp. I never heard any scary noises from the speakers. The sound just got compressed sounding and a little harsh. It may have been the limits of the amplifier. All I know is that I haven't had it happen since, because I do not normally listen at ear-bleeding volumes. I was mostly just playing around to see how loud it would go.