What Difference between Pass X150.5 and X250.5?

Eril, this can be a little confusing unless we define which generation of X-amps we are talking about. In the original X series the X-150 became the X-150.5 when Pass decided to add the blue meter to the front of the amp, which the X-150 lacked. Otherwise, the amp was exactly the same. I'm assuming your question is regarding the new generation of X-.5 series, which is a major revamp of all the X-series amps. All the new x-.5 amps sound terrific in their price range. What you get as you go up in the series is not just more power, but higher initial single-ended class A biasing for certain amount of watts. This is followed by a number of regular class A watts untill the amps go over to class A/B. Because of this the 250.5 will give much more of the taste of the Pass Labs X/A series amps. The dynamics, slam, transparency of the old X-series with the warmth of timbres and organic/liquidity often heard in tube amps. I have the 350.5 in my system and enjoy its virtues on a daily basis. The 250.5 will give much more of the above stated sonics then the 150.5, even though the 150.5 is terrific at its $ point the 250.5 is just that much better. Hope this helps.

Thanks Teajay.
I am currently using a Cairn Integrated Amp (first 10 watts in class A) with my Jean-Marie Reynaud Evolution 3 speakers. 88db sensitivity - easy to drive but do better with high current and high damping factor.
The speakers are well banced but a tad soft/warm.
I like the Class A sound better than any AB or valve sound I have yet heard and I thought the new Pass X-5 series was a good potential match.

I assume the new Pass ".5" series of amps was only from the X250 and up, i.e. the current X150.5 untouched correct?