Welcome Bigdaddysteve

SET amps were the first amps made in 1930s, they are plain simple more simpler than PP, few parts. According the great Gizmo after 10W tube amps become more complex, more parts, more expensive etc
SET amps have best sound than PP due just 1 output tube and few parts, fewer joint solders etc
Decware built philosophy also apply here.
You may choose tubes according your Watts requirements:
300B 7W (a expensive tube)
EL34 7W (in Triode)
KT150 20W (in Triode, expensive)
6C33 13 to 15W
GM70 25W
All conservative SET projects, forget 211 845 805 they are expensive tubes and cant reach GM70.