Markus, the change in the design in of this amp was all Paul's idea. I seemed to be having problems with the combination of the 3C24 tubes and the other small tubes the 3c's worked with. I only started using tube amps a few years ago, I went from a VAC PA 35.35 to an SET 300B (which I still have, and which Paul worked on first for me).
As far as its power output, I guess I never asked, but in its first design (the 3C24), it put out around 11 Wpc. This amp seems to have a good bit more power now, compared to its previous iteration.
As I've stated, I am extremely satisfied with this amp in its current configuration, and I will live with it gladly for the rest of my days.
Regards,
Dan