SET the best?

@hanaleimike

Over the years I have owned many Tube amps. (Anthem Integrated One, Amp One, VTL MB-450's, Zesto Eros 300's, and Prima Luna.) The best sounding one was the Zesto Mono-blocks. Push Pull pure Class A. However, they are very expensive and being Class A plus Tube. They run very, very hot.
My experience has been SET does not always equal the best sound. It depends on your speakers, room, and program material you like. Both the VTL and Prima Luna designs offer switchable SET functions.
What you gain when in SET mode, is more sweetness. The upper mid-range and treble have more emphasis lending a more realistic, natural sound to vocals. Mighty good stuff if your music library consists of Singer-Songwriter, Bluegrass, and vocal centered Jazz.

The down side is, the lower end is not as well defined, tight, and punchy. If you listen Rap, Hip-Hop, large scale Symphonic, Rock, or EDM, you may find the bass lacking or too mushy.
The other consideration is the efficiency of the speaker you like. A lot of the 300b designs like the Decware Zen are a very low  2 to 6 watts. Depending on the model. So you will want to mate them with something from Klipcsh or Tekton. Anything that very efficient with stable impedance should work. Nonetheless these flea powers variants are probably not the best choice for a Maggie LRS.

Whatever you get into you will want audition and make sure it fits your tastes, speaker choice, and you find that SET sound is to your liking.

The amps I currently use, I hardly ever put them in triode. The music I listen to is very bass heavy. Thus the CDs and Albums I play soud their best when I have my amps set to push-pull. When I put on Diana Krall or Alison Krauss then I switch my amps into Triode, for a more palpable presentation of their performance.  

The price of the Audion is $7500 Pair, we did not change the price since January 2020.

As with all amps, power supplies are critical to best performance. My custom built 300B monoblocks each use power supply one generally sees in stereo amp. Larger, better ps equals more filtering-resolving powers, reserves of power-transient, micro and macro dynamics. Add in some silver internal wiring, hand output transformers, no soft romantic old fashioned 300B sound. Actually nearly the equal of my 845 in most of impact related sound qualities. Hard to believe when you compare 845, 300B power supplies. 300B  power supply looks silly small in comparison to either of my 845's. Again, power tubes make large difference in SET, some romantic or old fashion sound, others modern sound, more linear.

I agree, SET will never be objectively best topology, just as any topology isn't. Each person has their own values as to what sounds best. Certainly, speaker choice is more limited vs higher power amps, although continually seeing introduction of more high efficiency speakers over time.

Mozartfan-

The “tube” in the AGD Audions contains the proprietary GaN output stage.

The glass envelope facilities heat disbursement and can be easily replaced with future improvement. 
The GaN module used is the only such chip developed specifically for Audio.

AGD has just come out with a stereo amp called the Tempo. It uses a aluminum chassis cut from a solid billet. It is a more conventional design without the “tube” but utilizing the same technology. I believe the price is $5400.

Thus it differs from any other GaN based amps. I believe my explanation is accurate.