Best way to spend $1000 on used bookshelf speakers?

May take some time but Ref 3A de Capo i's can be found for around $1000

See Underwoodhifi END OF SUMMER SALE 

  LSA-10 Signatures Only $999.00 a pair Our lowest price ever Save $1500.00 36Hz bass from a monitor that sounds like a floor-stander

+1 @tweak1 on the LSA-10 Signatures — that’s a ton of excellent speaker for that price. 

I acquired a large monitor I had enjoyed years ago when reviewing it for Dagogo.com, the Wharfedale Opus 2-M2. It has similar wonderful 3" soft dome midrange that has appeal in the ATC and PMC speaker lines. I got my pair for $750 and have them mated to subs. I bought them specifically for the 3" midrange, because that sound cannot be duplicated by other smallish bookshelf speakers using different configurations. Now, I have a dynamic speaker utilizing the 3" soft dome mid and it is set up to perform as a larger floor stander. Nice result, as envisioned.  Best inexpensive speaker system I have used in quite a while. 

The Opus 2-M2 is rare around here. I hadn't seen one for several years, so when it became available, I moved quickly. To obtain similar outcome you may wish to consider an older PMC or ATC speaker.  

Vandersteen VLR's are my pick.
Made to be near corners, like true bookshelf speakers.
CT or non-CT they can really be made to rock. Just add a Belles Aria Integrated, some good Audioquest cables and you're set.
I use mine like monitors in my office and am very happy.
Bob