Alternatives. For €20'000/pr, I knew of Ilumnia's Magister which Marja & Henk reviewed in September 2018. I wrote up the €14'500/pr Vocalis monitor a year later. Either model features a bullet tweeter suspended on a stalk above the center of an upfiring mid/woofer which loads into a ported cab of stacked Ply. Ilumnia's USP is their unique main driver. That does away with a traditional rubber/spider suspension and its distortions. My own reaction hadn't been quite as enthusiastic as that of our late Dutch reviewer couple. It certainly hadn't struck me as deeply as the Bayz did now with its conventional mid/woofers but of course my systems had undergone refinements since. The Belgian designs mirror the Bayzs by clustering their drivers in close proximity and pursuing (mostly) omni radiation to differ from coaxial/triaxial solutions à la Cabasse, KEF and Tannoy. To my ears, Courante 2.0 was in a different league than my Ilumnia loaners had been but of course also demands significantly more.
Franck Tchang's €13'900 Avantages Audio César had been a full omni like the Bayz, albeit with twin custom widebanders augmented by a separate woofer and optional super tweeter all loaded into Duevel-type dispersion lenses. Whilst the 360° dispersion's effect on tone was the same, the French speaker hadn't been as dynamically liberated and its bass not as potent as today's Hungarian. Also, you'd get 3 pairs plus change for just one pair of Courante. That said, like the Ilumnia Vocalis/Magister, the Avantages César is a legitimate alternate option to the Bayz where shared design goals are concerned.
The most obvious competitors other than German Physik and Duevel—the latter's Sirius Be at the lower right demands a similar €40'000/pr—are the various Radialstrahler from mbl whose model 101E asked $45'000/pr when Michael Fremer reviewed it in late 2004. Very much unlike the Bayz, the mbl is a far more complex 4-way with 105/600/3'500Hz crossover hinges that requires biwiring and punishes amps with a low 81dB/2.83V/m sensitivity. Even if it sounded as good as the Hungarian, I'd favor the latter's more benign load, simpler 1st-order 2kHz 2-way filter and far lower mass where the 101E weighs 176lbs. Looking at Stereophile's step response of the mbl, one spots multiple rises across a 7ms time window, not the singular rise and instant settling of the Courante 2.0. That suggests a certain amount of time confusion as is common for complex multi-ways.
Probably close to the aural Bayz aesthetic is the Diesis Audio range of open baffles augmented by horn-loaded tweeters; and the full-range Alsyvox ribbons. That's based on noting how Manhattan's Rhapsody Audio dealership carries all three lines and currently is spawning franchises in high-income locations across the US. Their speaker lineup seems quite a natural when earlier already I'd made the sonic connection with dynamic open baffles and thin-film planar designs¹. Where those differ fundamentally is their figure-8 dispersion pattern. That effectively subtracts a room's side walls from the reflective equation due to out-of-phase cancellation. With Bayz Audio, there's true 360° pure in-phase radiation. Not exactly a club of one, their residence on the audiophile city map would seem to have just a few other tenants to be quite exclusive. A distant relative from another mother might be Alain Pratali's forthcoming Aurai Audio Zero Junior. That will feature back-to-back horn tweeters, an open-backed Supravox widebander plus a 4th-order band-pass woofer for omni dispersion though not fully in phase. Regardless, this is a very quiet part of town few will have visited before.
¹ As it happens, Zoltán won 2006's Technology Prize of the Hungarian Design Award for full-range electrostatic speakers "which represents the highest recognition in the field of design in Hungary".
Contraindications. Where there's light there's shadow. If you adore maximum separation and use these in a big room, they won't be for you. Though each image center localizes precisely, its outer edges balloon, feather and merge into others. That has images seem bigger yet less specific. The usual emptiness between them is filled with atmospheric reverb dither. That is caused by your room across a bandwidth far broader than usual. It takes no math to realize that this increases its percentile makeup of the overall sound. The result is a lessened difference between recordings. You'll always hear different musicians surrounded by their own venue cues but placing the lot into your very dominant fixed and now activated acoustics creates a certain sameness. You'll have different performances but always in the same concert hall: your own room. It's obvious but must be stated since it can't be turned off.
Then there are listeners like myself who fancy capacious stage depth. We deliberately move our speakers as far into the room as décor and practicality allow. Then we toe them in steeply and sit rather close. It's all done to minimize room interactions and make direct sound dominate so quite the opposite of Zoltán's approach. With Courante 2.0, moving too far from the front wall creates sufficient time delay between direct sound vs. its reflections that the latter begin to register as secondary shadows. This limits the practical depth one can achieve from purely physical distance before the 'church effect' kicks in. Finally more blended watercolor transitions are a different gestalt than what most audiophiles understand by maximum transparency and resolution. All these are aspects where Courante 2.0 begs to differ. For some it will mean full illumination, for others it could include certain shadows or dark spots. It's really a different approach, goal and aural aesthetic. The most basic market overview knows them to be in the severe minority of what's on offer. Make of that what you will. At the very least you'll concede that for most listeners who come from direct-radiating box speakers, these will take some mental adjustments of expectations and references. Whether afterwards all else will sound wrong; less to certain degrees; or fully correct instead and these wrong. that'll be up to each and every individual.