I had a similar experience, though the other way around. I was listening to some speakers at a relatively high end store (they sold 10k$ CD player power suppli

I had a similar experience, though the other way around. I was listening to some speakers at a relatively high end store (they sold 10k$ CD player power supplies, along with a selection of more reasonable gear), where they'd only have one set of speakers in the room at a time to prevent passive effects on the sound. (which is sort of reasonable, but a lot of work). So they bring in the Magneplanars and the (incredibly inappropriate) amp I was interested in, wire them up, and within 5 seconds I know they're out of phase, and then in another 30 seconds, pretty strong clipping. Sales person was going on about how good they sounded.