Pass 150.5 vs. Pass 250.5 ?

depends on what kind of music you listen to and the levels you like listening at.
Can you e-mail Focal and ask them which of these 2 will be the most appropriate?

In my experience, the bigger amps will provide better control of the bass and will run with less effort and strain on high volumes.

Focal JMlabs speakers are very easy to drive, I'm driving a pair of Micro-Utopia's with about 20 tube watts. I think that the 250.5 may be overkill, the 150.5 would not only be sufficient but might sound better as well.

Jond, your speakers are monitors.
1027BE are floor standers. I don't see any relation between these 2 pairs of speakers. Your last statement is a bit confusing. Can you please expand on how the 150.5 may sound better than 250.5 on 1027BE?

Jond is right. At least partially. These Electra's can be driven even with 300B SE amp. I tried it at home with Audion 300B and I had quite good result with it. Very nice and open mid-range with quite good bass extension and excellent timing. The problem is that I am looking for much better and more authoritative bass control - one that I had with Bryston 4B-SST (which on the other hand was a bit closed in the mid-range). Therefore, I am formulating my question now a bit different: would I get these virtues with Pass Labs X-150.5 ?