I currently own a Tektron 2A3/45, MastersounD 300B, Art Audio 845 and most recently just sold an Allnic m311 (PX25). I utilize beautiful Coherent Audio 18's that have a similar level of sensitivity @ 98+dB. My listening room is a bit larger, but overall, this question is one that I have experienced directly for many years. But, before I actually post, I want to share that I have been reading blogs for many years, but have never actually commented as I find the audio journey such a unique and personal experience. All I can profess to do is share my own unique and individual direct experiences.
I love my Tektron 2A3/45. These low powered tubes built by Attilio in Italy are a wonderfully designed and built, very reasonably priced gem. The tubes (2A3 and 45) are to me the epidemy of SET sound. They deliver an open, airy, detailed experience that is intensely close to an intimate live performance. However, and for the record, there always seems to be a however, in some genres of music, they can just lack a complete and full body. For an intimate setting of both female or male vocalists, or even the delicate concert delivered by a cello, I find nothing even compares to these tubes. But, when I play a full orchestral rendition of a moving concerto, or a little rock and roll, they tend to fall slightly short in the arena of complete body and tonality throughout the frequency range. Please don’t mistake full-body with bass. When in a proper setup, this amp has plenty of fast, full lower frequencies which I have never felt lacked bass.
My MastersounD 300B however, is fast, dynamic and never has lacked for power, regardless of the demands placed on it from the style, genre or volume of music. It sounds more truly complete throughout the frequency ranges, but and here we go again, lacks that true SET quality. I know I might be committing audio Hare Kari, but to me, it does not have the detail or the delicacy of the 2A3/45 tubed amps.
The Art Audio (845) maintains more SET true nature than the 300B, albeit, less than the 2A3/45. It actually has a sound closer to my Tektron amp than the MastersounD does. It delivers amazing power with full body and a force that is not touched by either of its rivals. One of the many beauties of the Art Audio Carissa is that it does not overdrive the tubes and therefore does not get any hotter than my 300B tube gets. I know, once again, the comments seem hard to imagine, but when you speak with Art Audio you will understand their reasoning and why the amps do not get hot like most all other 845 amps. But, to me the 845 just lacks a little tonality throughout the dynamic range. Perhaps just a tad rolled off in the highs, especially compared to either the 300B or the 2A3/45 amps. It also loses just a touch of detail and delicacy found in the Tektron; however, it delivers amazing full body force and punch that is spine-tingling during a moving classical overture.
The Allnic m311 (PX25), so sorry, I actually have never heard the Audion PX25, but owned the Allnic for man years. Was a great amp. It delivered more punch, power and body than the 2A3/45, more SET like detail and delicacy than either the 300B or the 845. However, to me just lacked a little excitement. It always sounded good, very good, but rarely if ever stopped me in my tracks and caused that hold your breath pause that comes with music being played through a piece of art. Still, the Allnic is perhaps one of the finest amps I have ever had the pleasure of owning and a true joy to listen to as a daily driver. However, getting PX25 tubes can be a challenge. KR Audio is the only current manufacturer of these unique tubes and they only produce tubes when backorders are substantial enough to warrant the process.
This week I will be taking delivery on an Art Audio Jota, a high-current set of monos that delivers 20+ watts through a unique 1605 power tube. I am hoping that they deliver the “unicorn” I am seeking; SET like sound with a bit more punch. Until then, I am a spoiled audio aficionado that switches between my 2A3/45 and 845 as the music and my mood demands. What a great hobby we all have!