No....the horn monos come with EL-34s but you can use KT-66, KT-77, KT-88, KT-90, or 6550s. I have 6550s in mine and they are my favorite so far. The horn monos are great for rolling tubes.
Fritz is correct.....there is a QS amp that uses 8417s but its not the horn mono. Mike Sanders offered owners of those amps a conversion option.