@pfmaudio
Disclaimer: The answer to your question is, of course, it depends. Since in my opinion, it is easier to segment the amplifier side of the conversation than the preamp side, I will offer my opinion there to start. There is no comparison on power/wpc, apples to oranges. My observations are in the context of a system with appropriately paired speakers.
The Audio Note SE versions and/or the SE Silver or Silver Signature versions of their amps will subjectively exceed the qualitative purity of performance of the ARC Ref150. PP vs single ended. For instance, I would take a P1/P2 SE Silver or Silver Signature over the Ref150 for tonal purity and texture. I would take a P1 SE Silver Signature over a the base P2 PP or base P3 Tonmeister. You really need to pick the speaker and then the amp, especially since Audio Note has so many variations of a particular theme.
I may be out of step with others but I would NOT purchase an Audio Note preamp below the M5 or M6 level coming from where you are coming from AND, even then, I'm not sure I would prefer it to your Ref5se. I will readily admit though that I prefer Shindo preamplification over ARC and ARC over Audio Note, especially in the context of a price band, so I am clearly biased. (I also prefer the Shindo Cortese 300b over the Tonmeister by a wide margin. Ive owned both and don't have any axe to grind.) I recognize that you are in Portugal and Shindo may be extremely difficult to source there. You may feel completely different though. For giggles once when I had the REF75se and Sasha 2's, I connected my 9wpc OTO SE Signature to the Sasha's and all the superlatives applied: the tone was superior, the bass was more musical, the midrange simply amazing. Normal listening levels...I was quite surprised. Now I'm not recommending this combo, it just showed the commitment to the Audio Note power supply implementation.
In short, if it were me, I would pick the new speaker, see how it sounds with your ref5se/ref150. Then drop in a demo audio note amp (or Jadis or whatever pairs best with the speaker you choose) of your choosing with the speakers and your ref5se and see how it sounds. I believe the ref5se is pretty special and you will have to spend alot of money in the Audio Note line to potentially exceed its performance. I say potentially because if the ref5se were being manufactured today, it would be a $15-20k preamp, its versatile, its fully balanced, it is warmer than current ARC pres, it has a really nice and linear remote volume control. It would be the flagship preamp for many manufacturers today.
I hope I didnt confuse the issue more but I would be remiss if I didn't strongly communicate that the strength of your present system is your ref5se.