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

Sergei - I would strongly advise you to email or call Pass Labs and ask them about the 110V/220V issue. IME, their customer service is excellent, and the information they give you will be definitive.

Also, I suggest you read Teajay's reviews of the Pass amps he's owned. They're illuminating and may help you make a decision.

Bryon

Another great resource for Pass questions is Mark at Reno HiFi. You might contact him, with your question, and about demo deals, etc.

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