I'm running my Sophia II's on Pass Labs XA25 amp. I've run them on Conrad Johnson Premier 350, ART 150 SA, and Premier 12's and Pass is providing the very best sound. I was using Acoustic Zen cables with the CJ and it sounded excellent. The CJ did not like Transparent Audio- The Wave Ultra's, but Pass prefers them. I am wondering if anyone has any suggestions for gaining more depth since the Pass provides all of the detail. The Sophia's have responded very well to the used pair of THE WAVE ULTRA's and I'm happy to keep them.