I had a Parasound A23 and A21+. The A21+ was rather good, though a little too warm for me and not as detailed. I got a KRELL Duo 175XD to replace it and it was much better for my tastes. Ultra smooth and more detailed, slightly less warm.
At that time, I also had a CODA #8 v1. It was not as detailed or smooth sounding as the KRELL. The smoothness is not usually something I look for but on the KRELL it was a nice sound. The CODA seemed better in every way for my taste’s vs the A21+. I liked the KRELL a little bit more than the #8.
I now have the CODA #16 to replace the #8 and KRELL. Not sure if the CODA #16 is better than the KRELL. They sound different. The KRELL is smoother, and the CODA has a bit more detail and maybe if I remember correctly a bit more bass slam.
I need to buy 1 more amp since I am down to 1 amp with 2 systems. Luckily, I am broke, so I am thinking instead of buying. I am considering the CODA #8, the upcoming Sim Audio North Collection (for neutrality), Bryston 4B3, and Mitchi S5. I am not considering the KRELL Duo XD because I do not think I would like it with 1 of my 2 speakers.
No tubes for me in either of my 2-channels systems. I use a tube amp for headphones. My 2-channel preamps are uber neutral and let the amp dictate the sound. I have a Benchmark LA4 and Holo Serene preamp. I have heard the LA4 with all the amps mentioned before. I did try a Schitt Freya+ tube preamp and it was not to my taste, nor was the CODA 07x preamp which is described as tubey.