Great question for Pass Labs or Reno HiFi. You should try contacting them directly.
I have the XA160.5 driving the Magico Mini 2 (4ohm, 86dB). It is a very difficult load but my 160.5 seem to be more than powerful enough. My room is only 16' X 15' X 7.5'. The needle never moves indicating that it does not leave Class A. It actually did move once, slightly, during the Sheffield Drum Track LP at full volume. I have heard the the 600.5 but not in my system. They, too, are very powerful. I think it will come down to whether or not you want to remain in Class A. I don't think either option will run out of power unless your room is huge and you listen extremely loudly.
I don't know how the subs would effect things. I would expect the soundstage information to change with the subs on, but are you sure that that fact alone indicates that you don't have enough power. You should be hearing more low level room cues with the subs which would change the perception of the soundstage.
I was at an audio club meeting at a Pass dealer this past weekend, and he offered the following: There is little difference between the Class A Pass amps and the A/B Pass amps, other than the biasing. Even the Class A amps will move to A/B mode beyond a certain point, so that their peak output capabilities are much higher than the Class A power rating would suggest. He remarked that it almost doesn't make sense to sell the A/B models unless there is a regular need for extremely high output power, like very inefficient speakers in a large room.
Bondmanp, those with more restricted budgets might argue that ...it almost doesn't make sense to sell the A models unless there is a regular need for extremely low output power, like very efficient speakers in a small room. :-)
I have owned the XA160, X600.5 and XA30.5 and ended up preferring and keeping the X600.5. The X.5 line is of course more powerful than the XA / XA.5 line, and I'm sure you know that. But there are other differences in the character of the sound which must be taken into account. The XA / XA.5 line is sweeter, darker, more relaxed and mellower sounding, whereas the X.5 line is faster, livelier and more dynamic sounding (greater PRAT). I find the XA / XA.5 best for vocals and small ensemble music (jazz, folk, classic rock, etc.) , whereas the X.5 is decidedly better for large orchestral works which is the bulk of what I listen do.
I could have very happily lived with the XA160 as well. OTOH the XA30.5 was very underpowered even when driving highly sensitive speakers for the type of music I listen to.
Bottom line is you must listen for yourself because it is very subjective.
How would you think the Xa200.5 measure up? Compared to A set of X1000.5 amps.
I've owned the X600.5 and now have the XA200.5.
As good as the X.5 series is, it sounds hard and 2D compared to the XA.5 series. For large orchestral pieces, the suitably powered XA.5 series wins easily because the climaxes remain sweet and undistorted. The X.5 gets harsh and glassy at peaks.
There were some changes from the XA to the XA.5, which I wonder may have resolved some of the issues with peak distortion and the sense of unlimited power reserve.
I've posted my thoughts and descriptors of the XA200.5 on the forum if you do a search. The descriptors remain true even today. In my view, the XA200.5 is a masterpiece, with the only downside of heat. My amps are the muscles in a synergistic combination with key components of preamp and cabling. As good as the amps are in isolation, the BAT, Jade, Tripoint, NVS Sound combination has taken things to another level.
It comes down to personal preferences. Some people swear by the dark, liquid, and velvety sound of pure class A, while others prefer more neutrality, speed and dynamics. The question isn't whether the XA200.5 is sufficiently powerful, it's that it sounds fundamentally different in character from a class AB design. Some people, myself included, actually prefer the latter, as do the many people who buy state of the art class AB designs from ARC, MBL, D'Agostino, etc
If your X600.5s were exhibiting glassiness, it was probably caused by component matching, AC quality or cabling.
I will soon have a pair of Pass labs Xa-200.5 to a/b against a New pair of Pass labs X1000.5 I will Post some thoughts Soon. Thanks for the replies.
Gary, That will be a most interesting comparison and I look forward to your report. May I ask what is in the rest of the system?
I found the Pass Labs XA200.5 amps to be more Musical. I would say the 200 watts of class A sound make a huge impression. With the X1000.5 there was more Bass control.
I found that the X.5 really benefited from an extended warm-up time. It took at least 8 hours for it to become musical and listenable for me. At 12+ hours, it was even better. During the winter, I would leave them on 24/7, and they sounded good. During the summer, forget it. However, the XA.5 sounds better cold than the X.5 after 24 hours.
For the XA.5, I think there is some small improvement after 2-3 hours. There may be additional subtle improvements after 8-12 hours, but these are quite minor. If someone was coming over for a listen, I'd leave the amps on overnight to get the best sound, to be sure.
For bass control, I think this can be optimized by component and cable matching. But the X.5 would probably have more "fast" bass.
Gary, Thanks for the update. Are you keeping either amp for your system and
may I ask which speakers and pre amp you use? I had an XP-30 in my system
for a week with the XA160.5 and XONO and really liked this new preamp.
I kept the Xa 200.5 amps over the X1000.5. They are so much more musical. I find that all the recorded and store bought cd media have so much more information. I mean They sound so much better. My system is in a whole new level of sound. Scary Magical after a short warm up.
At comparable price points, I agree it's purely personal preference. Despite what's often written, Class A is not preferred by all listeners, as Petrushka points out, and the XA amps are more powerful than their ratings suggest.