Denf, I now have lived with the Pass LabsX-350.5 for a year in my system, and am still as thrilled with its sonics as I was when I first auditioned it in my system. It replaced a pretty damn good amp in its own right, EdgeNL-10, because it offered a more "natural/musical" presentation, often associated with tube gear, but with all the details, slam, and clarity of solid state. And yes, the .5 series is a significant improvement over the first generation X series by leaps and bounds sonicly. I never really liked the original X amps, auditioned them when they were released, and kept my Pass Labs Aleph 1's untill the Edge replaced them. The .5 series returned to the "musicality/liquidity" of the Alephs but added clarity, details and great slam.