going Pass Labs, do I need "Class A " ?

Petrushka, That seems like a good summary, though I haven't heard an X.5 amp
in my system. How would you describe the slightly different voicings? Is the
difference fairly subtle or quite noticeable? Thanks.

The XA.5s are sweeter, darker, more liquid, palpable and mellow/relaxing. The X.5s are livelier, faster/snappier, subjectively more dynamic and punchy. In terms of bass the XA is warmer and more diffuse (but not untight or lack control) and the X is leaner and tighter.

I'm speaking purely in relative terms as all Pass amps are sweet, dynamic, etc compared to the competition.

I like the XA for jazz, classic rock, etc and the X for massive orchestral or choral works, not so much because of reasons of power (the big XAs have plenty) but because that's how they are most tonally suited.

Thanks for that description, Petrushka. That makes a lot of sense. I think it would also depend in large part on the speakers and how they are voiced. Some are warmer and more relaxing and some are more dynamic and lively, etc. Also, on a listeners personal biases and types of music as you write.

I'd love to directly compare the XA160.5 to the X600.5 in my system. It's tough though with no local dealer and shipping costs for such heavy pieces.