Sorry, Null1 and Jeffjazz, no one is attacking your first generation X-series amps, but time and Nelson Pass marchs on. I owned and enjoyed for over nine years a pair of Aleph 1 monoblocks in my system. When Pass Labs came out with the X generation series I audtioned the 350 and admired its dynamics,details,transparency and extension on the top/bottem, but found the amp to be not as musical or natural sounding as my Alephs. However, the new X-.5 series is a beautiful blend of the warmth/musicality of the Aleph series with the wonderful above mentioned virtues of the X-series. If you heard the 350 and the 350.5 side by side you would hear the difference, and realize it is signficant in nature. Your amps are still great pieces and it sounds like you guys love them, however the new X-.5 series is another step towards the reference of live music and proves again that Mr. Pass is a pretty bright fellow to say the least.