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

I saw it the other week and almost pulled the trigger. Glad you’re enjoying it!
Aric is great to work with. I have one of his preamps in my secondary system,(The Unlimited),that I purchased new. I had a question regarding the ML II, even though I had purchased used,he still responded within 10 minutes.  

Please tell me about your experiences with the F4 amp driving what speakers and from what line stage.