The SE bug hit me a long time ago around this time of the year. I went into an antique store and heard Xmas songs playing and was pulled to the back of the store to find an old Philco Radio console. I could not believe how nice it sounded. It used an SE hooked up to a 45 output tube pair. Just beautiful liquid sound. I went back later and was going to make an offer and it was gone. So not just a 300b but 45's and other output tubes will work as long as the system is efficient no matter if it is a folded horn or bass reflex with mid and hi freq horns.
Alexc; the output transformers you show seem very expensive. I'm sure the design on the philco radio was no where near that design but If you want to use them to mix on(as well as listen), it might be the way to go.
In that price range I would look at these as well.
http://www.ebay.com/itm/300B-SE-tube-output-transformer-one-pair-Similar-Western-Electric-171A-for-91A-/121520933907
They look like they might be good for the 300B application.
Alexc; the output transformers you show seem very expensive. I'm sure the design on the philco radio was no where near that design but If you want to use them to mix on(as well as listen), it might be the way to go.
In that price range I would look at these as well.
http://www.ebay.com/itm/300B-SE-tube-output-transformer-one-pair-Similar-Western-Electric-171A-for-91A-/121520933907
They look like they might be good for the 300B application.