Preamp Recommendation for First Watt F4

I am planning on building a First Watt F4 because it would be a good learning experience and, by all accounts, it's a great amp in the right system. Can anyone provide specific recommendations for the companion preamp? My guidelines are single ended, 20+db gain, and preferably tubes. Not ideologically opposed to solid-state, but think tubes are better fit in general. My short list:
CJ ET7s2
Aric Mother Load II
Allnic L7000

Thanks