When I owned the XA60.8 followed by the XA160.8 paired with the XP20 I could not understand why two fantastic amps could be so underwhelming. I replaced the XP20 with the XP30 and still was far from impressed. Could it be the Pass preamps?! I inserted the XP30 into a friends system that consisted of an AR Reference 5SE paired to Parasound mono’s which at the time sounded great until I heard it with the XP20 and too fell flat and lifeless. Out went the Pass preamps and in went a tube preamp, in my case the original Aric Audio Motherlode tube preamp and then and only then, the big Pass amps sang with detail, richness, body and weight that the anemic Pass preamp failed to pull out.
Pass-great amps, not so great preamps, I am afraid. All of my fellow audio brethren who have convinced themselves that the Pass pre and amp pairings afford them the most ideal combination are, in my humble opinion, have been duped. Get a tube preamp!