Must speakers have certain volume to sound convincing ?

Inna,

Too bad you are not impressed with Getz and Gilberto.   Everyone has their preferences.  I happen to like the music, the playing, and the singing, but that was not remotely the point of my post.

The music/playing/singing is a matter of taste.  The SQ on the both the SACD and the Analogue Productions 45 rpm LP is not.  (The former was playing when I heard the SoundLab system that so impressed me.  I own the latter). By virtually anyone's standards (assuming good hearing), it's a very good recording.  By most people's standards, it's better than that.  When you've heard the recording on a well set-up SoundLabs system and still find the recording unconvincing, let me know.

Til then,  I'll file your comment under "not my taste in music" rather than as any kind of informed judgement on panel speakers.

I've found that different recordings have a loudness sweet spot where it sounds right, Peter Walker of Quad fame said this many years ago.
That sense of aliveness with all its tonal colours and dynamic shading is gold when it isn't driving me from the room, you know what I mean when your head is trying to tell you this is great and your heart is hiding under th couch, maybe that's what fatigue is.

Should i make a you tube video for evidence panel speakers can play loud ? 

I think it is more about how loud you want your performance to sound. Scaled back, intimate, or lively and present. Some systems can pull both of these off, but me personally, if it is good, I want to turn it up  :)

I particularly like horns because they can sound dynamic, lively, and satisfying at quite low volume levels. It is just a guess, but, I bet that is part of the reason they are so popular in Japan where everyone lives close together and no one wants to offend or inconvenience their neighbors.

I think there are quite a few panel speakers that sound VERY realistic and are capable of playing at respectably high volume levels. I would never categorically exclude them from ANY list for any particular performance parameter, except perhaps, compatibility with very low-powered tube amps (Quad 54 fans might disagree on this exception). Can soundlab U-1s rock, or Sanders Sound Model 10 or almost any Maggie? You bet they can.

Different drivers as well as different architectures will play at low levels differently. One of the reasons I’m a horn-guy is because of the remarkable (in general) resolution at low listening levels. The fact that they can go out to "ffff" as well is an added bonus.

Many electrostats can do the low level thing as well. This isn’t about panels however. The older Magnepans needed a solid kick in the rear in order to come to life. They sounded a bit dull at low levels. I haven’t heard their recent efforts.

Low level listening (and whether it’s important to you) is frequently overlooked, and in no way am I diminishing the importance of playing at realistic levels, but let's be honest with ourselves - how often are you going to play The Who's "Live at Leeds" at "correct" SPL's?

Cheers,
Thom @ Galibier Design