I went to the general "speaker" forum and did a search on "Arpeggione". 37 posts showed up, some which included people talking about which amps they used. In one the poster was talking about his 140 watt amp that he used to drive them.

Some of the people on this forum are into running under 10 watt amplifiers which power their speakers fairly loud. That's because of the efficiency of the speakers. Note: the fact that speakers are really efficient doesn't mean they make good sound, it just means it takes less power to drive them louder.

Grant.