Best Cheap, Small, High Sensitivity Speakers

B&W DM302. Recently discontinued, but many mint pairs available for as little as $175. rated at 91. Stereophile Editors Choice speaker and was EISA loudspeaker of year for 1996 and 1997. Check here and on eBay.

Triangle Zephyr or used Triangle Ittoh.

Look at Zalytron.com's high-efficiency kits, they have one called the Mars that may be what you need.

Try Soliloquy 5.0 monitors. I had a pair, and they were
terrific. They make an identical speaker with higher
sensitivity specifically for SET amps and other low
powered amps. I can't remember the exact model, something
like 2A3, but don't quote me. They have a very natural
midrange, bass rolls off below 45Hz (typical for a monitor)
but mates well with a subwoofer. Imaging and soundstaging
is outstanding. I sold my pair in excellent condition for
$475. I think they're $895 new. The 2A3 model has something
like 93dB sensitivity. The 5.0 model is around 88dB.

Triangle Acoustique Titus - Rated at 90db. Very easy load.

Also, Soliloquy SM-2A3, specifically designed for SET, recommended amp power is 3-25 watts. 10ohm speakers. A bit higher than the $1,000 mark, but a pair just sold here on AudiogoN for $850 with stands!