SST Son of Ampzilla ll power amp vs Classe Sigma Amp2 power amp

I haven't used one but my very good friend and audiophile buddy used one for many years.   He was very pleased with it, which is saying something since he has a great system.   I am not sure if he still has it or it was retired for something bigger.  I know he has some big monoblocks in his system now.   I'll have to ask him and update this posting.

I am using the Son II with my Harbeth Super HL5+ speakers and a tube preamp. Curious what is prompting the desire to change as you say you have been happy with the Classe amplification. Is there something you are trying to achieve that is missing?  I have no experience at all with the Sigma or any other Class D amps, have had class AB amps only for a long time. I personally have not found huge differences between quality AB amps - the SST replaced a 200W Meridian and that replaced a 150W integrated (from Classe actually) and I was quite happy with each and found any differences quite hard to describe. That said, I am going to audition the new NAD M33 for it's convenience and room correction (I have a very wide room) to see if it improves anything since I can do so risk free.

FYI Underwood HiFi has a few Ampzilla amps and Ambrosia preamp on sale