When Margin Walker of this parish put his Quad 909 up for sale I just had to try it with my ESL 63s. I was running them with my HackerNap. So the 909 was duly substituted for the HackerNap and the HackerNap is not going back. There just seems to be a synergy between the 909 and the Quads. The only way I can describe it is that the 909 has more complete control over the ESLs which makes everything sound completely effortless and natural. Midrange seems to be more filled out and small details are more noticeable without losing bass or top end definition. Others have said that the ESLs thrive on more power and this certainly seems to be the case with the 909 delivering 140W per channel compared to my HackerNap which will be up for sale soon. Rest of the system is LP12 with Mose and stack top plate/armboard, Ortofon 2m bronze, Nima, Arkless phonostage, B4 and Avondale Arcam Alpha5+ cd.