I own and use both, the Triode Lab 45 SET mono amps and the Triode Lab 2A3 SET mono amps. The link below will take you to our use of the Triode Lab 2A3 amps a show so you can read what was said about the sound. I find the 2A3 amps to be a bit more relaxed sounding and the 45 amps to be a bit more lively in our systems. Unfortunately it's not that simple because Frank has different output transformers and other parts to choose from which alters the sound a bit as does the choice of tubes (the whole tube set). Make sure your speakers are truly high sensitivity. Frank can talk you through how parts and tube affect the sound.
https://pt.audio/2019/06/28/the-return-of-the-arion-audio-apollo-system-t-h-e-show-2019/
Mike