I know this thread is old, but felt compelled to respond as I have experience with both of these amps. My previous amps have been Anthem, Proceed, Bryston, Classe, Cary, and Krell. My affinity with Pass Labs amps started with the X3, and then onto the X150.5. After living with the excellent X150.5 for a few years the upgrade bug bit again. Pass labs amps don't come up for sale often on Audiogon as they are a great value for the money. A X250.5 showed up and I jumped on it. I did an A/B comparison between the X150.5 and X250.5 after allowing each to warm up and the source playing for several hours. Me being the somewhat cheap bastard that I am tried not to tell any difference in sound quality, to justify the difference in price. I was using CD's playing through a tube pre amp with NOS tubes and Dynaudio C1 monitors. Although the X150.5 had provided many hours of listening pleasure, the X250.5 had just a bit more in some ways. Same clear presentation, but a little more slam. The clincher was the small nuances that I had never heard before. It allows me to connect to the music closer to a live event. The build quality and design are also superb.
