Best small used monitors under $1000

I second the KEF LS 50's

I had Neat Motive 3, Monitor Audio GX50 and Epos K5.
Then got PMC DB1i ... those PMC's blow them all away for me.
Simply amazing

I bought a pair of inexpensive LSA speakers that sound pretty good in my high end preamp going to Akitika power amp which I built for a few hundred dollars. Good enough for my casual listening. I have a mostly class A system for my listening (in my music chair).

For my snowbird home I bought a pair of used Revel Performa 2s for under 1k. They will be matched with a First Sound preamp and a Plinius P10 power amp and a serviceable Marantz CD player that I may upgrade at some point. The Revels are quite a bit better than the LSAs. Over the years I have upgraded my speaker and interconnect to Acoustic Zen through Audiogon. I do have basic Supra speaker cable in my casual system that sounds quite good for a very reasonable price.

Platinum Audio Solo
A pair comes up on here from time to time under $1000 with stands(which are critical).  They are a beautiful speaker that sounds amazing.  I have the Quattro tower and absolutely love them.  

Try Vienna acoustics Hayden, incredible sound when used with a powerful amp. They're pretty close to my VA Bach and Mozart