I have owned a pair of the Zu Soul Supremes for the past three years or so. I just melt in front of them during most listening sessions, wonderful imaging and soundstage width/depth. Proper placement (toe them in) and bottom gap height adjustment can optimize bass response. I changed the internal crossover capacitor to a Jupiter copper. Not sure why, just felt like messing with it. They are extremely efficient and the XA25 might even be too much power. I can use a 300 B or 2A3 amplifier and create ear splitting volume. The Zu SS’s sound great to my ears, but are well known to require some driver break-in. I’d buy them again in a heartbeat.