If you don't want to spend a huge amount of money the Klipsch KLF Series (10,20,30) sounds very good at 98,100 or 102 (dB). You could purchase Lowther drivers in a pre-built cabinet, or make your own. Same for the Hammer Dynamics 12 Loudspeaker kit, see: http:www.melhuish.org/audio/hammerdynamics.htm and http://www.enjoythemusic.com/magazine/equipment/0600/super12.htm There is a huge section written here on Audiogon about best speakers to use with 2A3 speakers or single ended amps. Sorry I don't remember the exact name. You could research it or perhaps someone else can assist!
High Efficiency Speakers
I'm building an affordable all-tube system, and I need to start with very efficient speakers so that I don't have to spend $$$ on a SET amp. I'm targeting a 2.5w SET w/ 2a3s tubes from Bottlehead. Consequently, I need 96db+ speakers. I primarily listen to accoustic guitar, classical, and vocals. What speakers would you guys suggest I listen to?