Mani-2, Roger Modjeski himself agrees with you about SET amps! He makes a number of different models of them, for use with high-sensitivity loudspeakers. But for use with low-sensitivity designs, including the OP’s LS3/5a and Tablettes, SET’s are often not the best choice.
Modjeski designs his amps for specific tubes. The RM-9 was for EL34’s, the RM-200 for KT88’s. The RM-9 creates 100w/ch from a quad of EL34’s per (the Mk.2 version 125w/ch), the RM-200 100w/ch from only a pair of KT88’s per! And that power is achieved not by running the tubes hard (which is common amongst other designers and companies, and which decreases tube life), but rather by creative engineering. And unlike every other tube amp ever made, the RM-200’s power output increases as the loudspeaker impedance drops! The exact opposite is the case in all other tube amps, including the RM-9.