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

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.

Mwilliams,

pre amp considered is Pass Labs XP-20.

In my present system there is ATC SCA-2 and I might as well keep it - !?