I also own a pair of S100's fed by my Music Reference 100W RM9 tube amp. I'm chiming in due to something I read recently that struck me as odd. I joined a Spendor chat group a few months ago. The son of Spendor creator; Spencer, posts there frequently and he, in no uncertain terms, says he absolutely does NOT like mating Spendor spkrs with tube amps. He's actually ambivalent about the subject, saying the spkr's were originally voiced using SS amps. I found it odd due to A) so many Spendor owners thru the years have had great results with tube amps but more to the point B) why would a spkr manufacturer try to dissuade anyone from using his product with ANY amp!? Go figure.