i'd check out hedlund horns - see:
http://www.adminsoft.ch/Hedlund/HedStart.htm
these can be quite reasonable, if you are willing to build them yourself...
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?