I used a 55x for several years. Plenty of power. Drove anything. Sounded neutral. Then switched to Dynaco Stereo 70. Completely different but lovely sound. Now have about a dozen amps including several tube, mid 20th Century, Class D, and others. Also several huge Yamaha AV receivers. And Denon POA-1500. Like a variety of sounds. Oh, and several early Sansui amps. I don't see anything really wrong with the 55x. It has its uses. A bit clinical for my main amp now. Like more character.
