Pass Labs comparison

I am considering a Pass Labs amp to power my Martin Logan Summits (Summits have internal amp for base). Currently using Rogue M-150 amp. Currently on Agon there is a Pass Labs 350.5 for $6,000, a 250.5 for $3,500 and a 150.5 for $1,900. Are there any differences between these amps other than the power? Do you think the improvement generated by the additional power justifies the incremental cost? If so what kind of improvement can one expect? Thanks for your thoughts.
I have not heard the new generation of Pass but would offer some things for your consideration. The first is the usual reason for increasing power is to get better bass, which does not apply in your case. Would the extra power be of use to you? The second is that with top quality amps the circuits are usually the same but with increased number of transistors , etc. The penalty for doing this is that it increases the complexity of the circuit. I recently faced a similar choice when I decided to buy a Musical Fidelity Integrated amp. I could choose between the Nuvista, Trivista, Kw500, or Kw550. There was a price differential of course but it was not insurmountable. In the end I chose the Nuvista as it had the fewest number of transistors and therefore the simplest circuit. It had plenty of power for my purposes and I am very happy. With an amp like Pass that runs class A all the way it would be hard to see how the bigger amp would improve upon the sound of the smaller one as long as it is operating within its power range. Also do not forget that the larger amps will generate more heat and consume more electricity. As a former Krell dealer I can tell you that this is not to be ignored, not to mention that large class A amps range in weight from very heavy to why didn't they put wheels on it.
These Pass amps are not pure class A. The more powerful amps will run in class A longer.
With an amp like Pass that runs class A all the way...
Stanwal (System | Threads | Answers)

The "X" series Pass Labs amps run Class A for about the first 30
watts, then switch to Class AB.

The "XA" series amps run 100% Class A.

I agree that buying the smallest amp that suits one's system is smart, for the
reasons specified by Stanwal.
According to the Pass website the X150.5 leaves class A and begins operating in class A/B at 10 watts, the 250.5 at 15 watts and the 350.5 at 40 watts.
The XA amps unlike most typical ss power amps loose power into lower impedance loads. The XA.5 amps are better suited to lower impedance loads.
One has to be carefull when discussing Pass amps, unlike most amp manufacturers, Pass amps differ quite a bit from other Pass amps. Choose your Pass amp(s) accordingly.
If you want it all in a Pass Labs amp, isn't the XA.5 series the way to go? 100% Class A and doubles output as impedance is halved.

I agree the model lines are confusing as far as what features they offer.
Unsound, as far as I know the new Pass XA.5 class A series does not suffer of the problem you mentioned. It is said to double power as speaker impedance is halved. G.
I would look to Ayre and Audio Research Also I might add, you have to LISTEN to all equipment - preferably in YOUR system to see if all is compatible. A component purchased on reputation, name, specs, etc. is pretty much sure to disappoint.
Having owned the Summits as well as driving them with Pass..The 250 will work but I always thought that I needed a little more with certain music. There is no doubt that the XA.5 is the way to go if funds will allow. ML & Pass is a great combo. Many people use it you can see it here: