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

I've owned two Pass amps, previously the X250.5 and currently the XA30.5. Their differences may be similar to the differences between the X350.5 and the XA60.5.

In my system, the X250.5 had somewhat better bass than the XA30.5. The XA30.5's bass is quite good, but the X250.5 controlled the bass almost like an active speaker, i.e. effortlessly dynamic and lots of headroom. On the other hand, I'm sure there are folks who would say that the XA30.5 has more *musical* bass. IMO, which amp has subjectively better bass is a matter of speaker compatibility, room size, listening volume, music preference, and taste. If you listen to symphonic music at 90+ dB in a large room with inefficient speakers... you get the idea.

In my system, the XA30.5 has somewhat better treble than the X250.5. The X250.5's treble was good, but the XA30.5 is slightly more liquid and more musical. With your speakers, I'd say that's an important consideration. Whether differences in treble are more important than differences in bass is of course subjective.

In my system, the XA30.5 has less harmonic coloration than the X250.5, though neither of them sound "colored." It's that the XA30.5 has more harmonic *variation* than the X250.5, which is perceptible mostly in acoustical instrument timbres and voices.

In my system, the XA30.5 is slightly quieter and has slightly more resolution than the X250.5, but both of those differences are subtle.

That's everything I can think of at the moment. If you mention more about your system, I might have more input.

Bryon

Bondman is correct. Stereophile's measurements of the XA30.5 confirm this...

While the XA30.5 may give 30Wpc into 8 ohms in class-A (14.8dBW), the distortion at this power level is low, at 0.015%. The amplifier doesn't actually clip (defined as the THD reaching 1%) until a much higher power level: 130Wpc into 8 ohms (21.14dBW). Even higher powers were available into lower impedances before clipping: 195Wpc into 4 ohms with both channels driven (19.9dBW), and 332W into 2 ohms with one channel driven (19.2dBW).

Having said that, there are design differences between the XA series and the X series that go beyond biasing. IOW, the XA series isn't simply the X series with a higher bias setting. And that is reflected in the difference in sound, IMO.

Sergei - I noticed you added the XA100.5's to your list of possible amps. IMO, that would be the best of both worlds. I've heard the XA100.5's, and they are glorious sounding. They are considerably more money, but you may be able to find them used. Reno Hifi is a good place to start.

Bryon

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