High Efficiency Monitors - List

No such thing...really. A few companies will cheat their stats or maybe go as far as not to give you any bass.

Set you goal at 85dB, and you will have much better choices and better sounding speakers.

Otherwise you should look at active monitors.

Small is inverse to efficient in speaker design.

Omega makes some fairly high efficiency small speakers (genuine 8 ohm load, efficiency in the lower to mid 90's) using modified Fostex and other fullrange drivers. You trade off bass extension and high power handling capacity.

D. Edwards is right - the inevitable tradeoff of efficiency vs bandwidth means that a small speaker can't give you deep bass and high efficiency at the same time. Whether the Omegas can give you "enough" bass depends on what you're looking for and how much boundary reinforcement the speaker gets. Of course bring a subwoofer into the picture and lack of bass is no longer an issue.

Duke

Reimer Speaker Systems, Reference 3A & previously mentioned Omega Speaker Systems are some companies manufactuering fairly efficient monitors that you might look into. Merlin might be another. But D_edwards & Audiokinesis are right, there are only a few unless you are willing to go DIY route & that only adds a few more.

See: http://www.welbornelabs.com/recomendspeaks.htm

IMO, crossover slope is the major limiting factor. Tubes do not like third & fourth order xovers & second order xovers should be limited to larger push-pull amps rather than flea watt SET amps.

You might want to check out some of the older Paradigm models (3se in particular). I think they were fairly efficient (90-91db), but they were medium-sized monitors w/8" drivers.

Check out the deCapos. Not quite as sensitive as you specify, but the easiest load any amp will ever see (single element x-over). Your max SPLs may be limited, but virtually any amp will drive these speakers to moderate volume levels.