If you're posting about SOTA loudspeaker manufacturers at the top of their game, you're opening up a can of worms as it is all subjective at this level. That said, imho Magico, Rockport, Wilson Benesch, Genesis Advanced Technologies, Marten and YG Acoustics should be on your short list. The best loudspeakers in the world at the moment imho would be the Magico M6, Genesis Prime, Marten Coltrane Momento II, Wilson Benesch Eminence & Rockport Lyra. You did say "best".

Best? Meaning what? Best build quality? Best sound?

There is a very old saying: "Perfection exists only in the mind."

Once you start spending serious money buying reputable audiophile components, you can expect reasonably good build quality. By definition, if you are an audiophile what you are really searching for is the best sound (i.e. as close to the live performance or recording session possible). That will depend upon the quality of the components in your sound system, how compatible or well matched they are with one another, the quality of the recordings or source material you are listening to and the acoustic characteristics of the listening room.

By all means, research the loudspeakers you are interested in, confer with other audiophiles, go out and do some critical listening to the ones that interest you, preferably over components exactly like your own or as close to that as possible, in a listening room as similar to yours, as possible, and with music or source material you enjoy and are very familiar with. Once you hear something that impresses you, arrange for an in your home demonstration. Virtually all reputable dealers of high-end audiophile equipment will offer, at least, a 30 or 60 day return policy to allow you time to hear loudspeakers in your own home, connected to your own components so you can truly gauge what the sound quality will be in your home. Give them plenty of time to "break in" and, then, your ears will be the ultimate judge. Feel free to have friends listen with you and give you opinions but, in the end, aren't you really trying to please yourself? Trust your ears! When all is said and done, that is the only thing that matters.

hat said, imho Magico, Rockport, Wilson Benesch, Genesis Advanced Technologies, Marten and YG Acoustics should be on your short list. The best loudspeakers in the world at the moment imho would be the Magico M6, Genesis Prime, Marten Coltrane Momento II, Wilson Benesch Eminence & Rockport Lyra. You did say "best".