The newest amplifier to the Allnic family is the A-2500, a pure SET design. It has a completely different circuit design from the former A-311M, featuring a new interstage transformer and larger power transformers on the stronger 2500 chassis platform.  At 20W SET, these will be the go-to amplifier for any speaker of 90 dB or greater efficiency.  The A-2500 is very spacious and outstandingly musical and emotionally engaging.  And - the bass presentation in no way left me wanting.  The 845’s low-frequency robustness is on par with my favorite power tube’s, the PX25..
 
A-2500 Monoblock Amplifier (Configuration at the factory only):
 
211 - 1st Stage 6CM7,  5R4WGA Rectifier and 211 x 1.  20W Continuous
Pure SET design.
 
845 - 1st Stage 6DR7,  5R4WGA Rectifier and 845  x 1. 20W Continuous
Pure SET design.
 
With the individual tube biasing, pairing is not necessary. Allnic circuit designs do not overdrive their tubes, and they tend to last a very long time. The M-2500 and A-2500 amps appear to retain this benefit.
 
To give you at least a rough idea of which of the “2500” monoblock amps might suit your requirements, you can find a handy calculator for amplifier power requirements for various speaker sensitivities and SPL at: 
 
https://www.crownaudio.com/en/tools/calculators#amp_power_required
 
Whatever choice you make, I am convinced you won’t be disappointed.  Both monoblock amplifiers are available with approximately a two-week lead time to delivery.  Introductory Price:  $18,000 USD.