For everyone here who is considering a zero feedback 300b amplifier, something you should know which has to do with the loudspeakers you plan to use: http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html
The short explanation is this: tube amplifiers with no feedback don’t adhere to the Voltage drive principles of about 99% of all loudspeakers made. That 1% left over are nearly all made by high end audio loudspeaker manufacturers. Zero feedback tube amps try to make constant power with respect to the speaker impedance rather than constant Voltage. This means if you mix the two technologies you’ll get some sort of tonal aberration.
In particular if the amp in question is also an SET, plan on having a speaker that is a bit more efficient! This is because all SETs that are zero feedback only have about 20-25% usable power- above that power level distortion causes the amp to sound ’dynamic’.
You might think that ’7 Watts is enough’; here’s a tip: Its the mark of the best systems that they do not sound loud even when they are. If a system sounds loud when a sound level pressure meter (available as an app for any phone) shows that it really isn’t, what is happening is distortion is being interpreted by the ear as sound pressure.
Put another way, if your speakers are efficient enough that the SET never needs to make more than about 25% of full power you’ll really start to hear the best of what that amp can do. In case there’s any doubt, this is part of why horns were so common in the 1950s and prior.