Planar speaker that don't require herculean amp?

I'm looking for a planar electrostatic or ribbon speaker, but they all seem to require gobs of power. I am currently using AES Sixpac tube amps with KT66 tubes, which have about 35 RMS watts each or so. I don't have to worry about low bass, as I am using a pair of Entec powered subwoofers. I listen to many types of music, but don't need incredible high SPL levels. Are there any planar speakers out there (preferably used) that can work well with my tube amps?