By nature of their sensitivity, they are high efficiency. As the 45 is my favorite, I think you should give 45's a try. Although I don't have druids, I do use 45's (~2.5W) with my 96dB sens speakers in a small room (13' x 11') with amazing results. I have 2a3 as well, both great, just a little different flavors. Have fun experimenting!
Cheers,
Brad