@dtorc FWIW, we make a 5-Watt/channel class A tube amplifier that can sit on a sheet of notebook paper with room left over. I designed it for my bedroom system.
BTW, something to keep in mind about SETs: if they have no feedback (and most don't), their actual usable power is about 20-25% of their rated power. This is because at power levels above that, the higher ordered harmonics start to show up on musical transients. This causes the amp to sound dynamic (since the ear uses higher ordered harmonics to sense sound pressure) but its really distortion masquerading as 'dynamics' and is the source of why so many people say SETs are a lot more dynamic than their power suggests.