I started with the widely acclaimed XA 30.8, then I moved to the XA 60.8s for the benefits of separate power supplies and more power. They’re connected in balanced mode and I’m also high passing them at 100hz because they’re connected to Vandersteen Quatros. My system does not need more power. These amps will also put out around 150 watts when called for. So given an efficient enough speaker setup, how could the larger Pass amps be an improvement? With more output devices, I’d think you’d get slight smearing of the sound in comparison due to the difficulties, if not impossibilities, of precisely matching ever greater numbers of output transistors. The lower powered Pass amps either don’t run in balanced mode or are not configured as monoblocks. With regard to the XA .8 line vs .5, the consensus seems to give the .8 line the edge. John Atkinson had said that the 60.5s were the best he’d heard at the time. The .8 version is the successor. Have I heard any of these other amps in my system? No. I’m just positing a theory based on extensive commentary.