My listening room is 15X16 and with the MiniWatt driving the OB Betsy's I'm getting peak SPL's in the mid 80db's at three quarter volume ( Norah Jones and Brubeck CDs ). The Betsy's are 3 ft from the back walls and 1 1/2 ft from the side walls and my sweet spot is 8 ft away with them toed in and crossing just in front of my chair.

My MW has the cap mod with Russian EV's and Western Electric 403B's. No diode mod yet. The Betsy's aren't nearly so SET amp dependent as the 4.5 Fostex drivers. The Betsy's are laid back, slightly less detailed but their huge soundstage is the hook for me. They would probably sound good with any decent SS amp. Before buying an amp you might want to try them with whatever you have on hand.

FWIW the MiniWatt takes a good half hour to sound it's best.