Ron,
I traded in a SET 120 for the M225's. The SET 120 is an amazing amp given its price and power rating. Very good midrange and non fatiguing top end. Imaging was excellent. The M225's kick things into another level. Dynamics, depth of soundstage, imaging, more lifelike and fleshed out details. I have a friend who owns a pair of Digital Amplifier Co. Cherry Maraschino mono amps. I think they are the King version with increased capacitance, etc. He allowed me to audition them in my system a few years back, when I still had a modified ADCOM GFA-5500 200 watt amp running my at-the-time Sierra-2 speakers (Now Sierra-2EX). I fell in love with those little black boxes. Unfortunately I was not in a position to afford purchasing a pair, so I ended up with the SET 120. The ADCOM was showing signs of parts failure in the way of whooshing noises from the left channel. The SET 120 came close to the Cherries, but did not have all the fairy dust those had. Before purchasing the M225's, I had been texting and speaking directly with Tommy O'Brien of Digital Amp Co and was seriously considering buying a pair of the maraschino mono amps. Unfortunately Tommy succumbed to COVID in November and the future of his company is uncertain, so that gave me the needed push to go with the M225's. These are not going anywhere!