What speakers are you using? That has a lot to do with what tube you can use. 2a3 amps are around 4 watts , 45 are something like 1.5 watts, 300b around 8
211 or 845 would be a high power SET....
I'm having a 300b built and its got a lot of options including vintage CTC power transformer and chokes along with Hitachi Fine Met Amorphous Core Output Transformers. I also have a pair of Quicksilver amps and Mike of QS has always used quality transformers so my 300b is getting the optional ones...I think it is what separates good amplifiers from great ones