Well, I finally got around to putting my Parasound A21 in my main system with my BAT Vk-51se preamp to compare it to my Pass X250 amp. I previously has the A21 with a Van Alstine Ultra Plus preamp.

There is no contest, the Pass amp is a much better sounding amp in most area's. The A21 did some things better such as treble which was a little more forward and the attack on guitar and piano was crisper. The A21 sounded faster as well. The Pass on the other hand has a much blacker background, is more dynamic, has a better midrange, is grain free and seems like it delivers a river of current when needed. It also has a smoother, more liquid, warmer sound with more depth. The A21 never runs out of steam as well, has great bass, tight, deep and fast but the Pass's is more explosive, more musical, while the A21's seems more dry if you will.

The A21 is a good amp but it is clearly out classed by the Pass.