5 years ago John upgraded the capacitors in my amps to help them drive my Thiel 2.4 speakers, the improvement was amazing. John has recently completed the final stage upgrade by replacing the transformers and adding even more capacitors. The impact has been transformational. They sound so much more powerful, I have depths of bass I could not ever imaging from the Thiels and so much more detail. The amps, which also used to heat the room are now cold in operation so I assume are far more efficient. I can’t recommend John’s upgrade service highly enough.