Small-ish Speakers That Come Alive At Low Volume

Disclaimer
I am a representative of a speaker line called "Role Audio"
One of the best small effective loudspeakers in the World. I highly recommend Role Audio FTL monitors. You will not be dissapointed, excellent in low vol.level listening with detail and the price is great - email for more info.

If you can find the old Red Rose Ribbon Monitor (version where the ribbon tweeter extends upward above the front baffle and cabinet), it's a good choice. Small, with great dynamics and real bass punch, although true bass extension is (understandably) limited and they're not entirely neutral in tonal balance. Overall, very convincing for a shoebox sized speaker.

Marty

I also love the Triangle speakers for top to bottom coherence and low level listening. I have the Celius ES in the livingroom and the Comete ES in the bedroom. The Cometes sound great at any sound level but are wonderful speakers to fall asleep listening to at low volumes without worrying about hearing loss. I have not heard the 3A De Capos.
John

I'm using Gallo Strada's in a nearfield setup with the TR-3 Sub in a small condo. Despite not being particularly efficient, they sound wonderful at low volumes. The presentation is very strong in detail and some might find it bright. They work well without the sub for some acoustic music, but are flat only to about 70 hz in my room.

Given your budget, I might suggest a few other choices:

Aerial Acoustics 5B
Harbeth HL-P3ES2
Joseph Audio RM7XL
Refernce 3A Dulcet
Spender SA1