How did happen to end up with your current amps?
There is only a handful in the USA. The American importer had too many problems dealing with China and dropped the line, and the North American Jungson importer is now based in Canada. I bought them used locally. However the aforementioned US dealer also carried Pass, and said they are comparable to the XA 0.5 line. My repair guy who had them in the shop and has heard a lot of high end gear also says bass control is the best he has ever heard. I personally have absolutely no reference to compare how good they are.
In retrospect I regret buying them because these exotic pieces are almost impossible to sell. In any case, I plan to wait for (a pair of) used spectral to show up - scoop them up and do a shoot out. If you get the spectral at the right price, you can resell them in a day with no loss in case I prefer my class A. Problem is waiting for used spectrals to show up. Other issues is you need a pair of MIT speaker cable for the spectral to sing.