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

the X- AMPS are going to be a better choice for music with more dynamic
properties; the XA-0.5 AMPS would perform better on subtler material- acoustic guitar, chamber music, female vocals, solo piano. if harmonics is- or will become- the most important factor in choosing what to listen to most of the time, then the choice is obvious. OTOH, in this forum some people have clearly become disappointed with their XA-0.5 amplifiers over time due to their changing of tastes, wanting more power and control across a wider bandwidth.
So you should ask yourself which path you're on.

French_fries, Are you saying the XA.5 amps have less control at the frequency extremes than do the X.5 amps? I always thought it was more about bias into class A and the distortion at the crossover point between the positive and negative halves of the signal. (How's that for a non-technical explanation). I'm curious as I'v only heard the XA.5 in my system. Clearly some prefer one line/series over the other, and visa versa.

Sergeik
you didn't mention what type of pre amp you were using,
I have the Sophia 1's and the XA30.5 in an 18 X 12 X 8 room. I had the Bryston pre but it didn't work well with the higher freq. but controled the bass very well, Last year i purchased the Vac Ren. mkIII and it made all the difference in the world. The bass is still tight,but there isn't any harshness in the tweeters. I couldn't be more satisfied with my system.

There is more than enough power in the XA30.5. the amp doesn't switch to A/B until about 98db. At that volume you won't here any difference.

Matt

dear mr. peterayer,
i am going by one person who put his XA-0.5 100W mono blocks up for sale. a lot of people questioned his decision in the forums, so
he explained at length regarding his changing preference for
a different design. apparently he felt the bass was lacking something in his system even though i don't think it was a lack of power.
just for an example i have levinson amps which don't inspire much emotion-
that has to come from within. but they do reproduce bass about as well as it can be done. i would think a pass X-.5 amplifier properly matched to your speakers would do the same thing. and bass can have a dramatic effect over the sense of depth / 3-dimensionality of the stage. OTOH they might fall a bit short on reproducing textural details of acoustic instruments or sound a bit flat on a Diane Krall album.
i have only heard pass aleph amplifiers - the 30 and the 1.2 mono blocks.
they were beyond reproach to my ears, especially on piano and jazz.
but i never tried them out on Bach organ pieces where i might have been
less enthusiastic. but i am easy to please when it comes to this level of audio gear,
so i could go either way without a 2nd thought and learn to be happy.

Peterayer, I hope you and French_fries don't mind, but IMHO dollar for dollar: yes. Though there are other considerations too.