Steve has consistently moved his products forward over the past 20 years by taking advantage of new/better parts, better circuit boards, and also through design changes in grounding, introduction of the Gravity Base, vibration control, Panzerholz material, and more. It is no surprise to me that he has come up with the Power Block upgrade, which improves the sound of his amplifiers by separating the power supply from the components amplifying the signal, as with his outstanding VRE-1 preamplifier and its outboard power supply.
If I were having amplifiers upgraded by SMc, or if I were in the process of purchasing their new amplifiers, I would not hesitate to include the Power Block upgrade. I wish I could give you direct feedback, but my DNA-1 Ultra G monoblocks were completed in 2019 prior to the Power Block upgrade. Fortunately, between having the Plitron low-noise toroidal transformers, star grounding, and Gravity Bases, my amplifiers are very quiet.
Here is an AudioCircle post about an SMc Audio amplifier with the Power Block upgrade. Just after 11 minutes in this interview, Steve touches on the Power Block outboard power supply. I hope you receive some responses here from people who have the Power Block upgrade but, if not, I suggest you ask Steve if any of his Power Block upgrade customers might be willing to speak with you.