unless your room is truly huge and/or you listen crazy loud, 60 push pull triode tube watts should be plenty (certainly 100+ pentode watts will be)...
mon 40’s work in the nearfield (take tom mallin’s experience with many grains of salt) but are really meant for decent sized rooms where their utter ease and big sound become magical, and the speakers can be placed away from room boundaries
that said, in my experience, the mon 40’s bring a good dose of richness and warmth to the music in and of themselves, and are best used with top flight solid state amps, as the big woofers and medium efficiency of the speakers like strong current drive and damping factor/grip for the best bass and uber clean transient attack
pass labs, hegel, classe (among other excellent solid state) are well known lovely pairings with mon 40’s