Best bookshelf monitor under $1000 new or used.

New AER Pisces MkIII - about $300. You must have good stands too.

You can drive them by Dynaco 70 or any other low power tube amp (20 - 50 wpc) - and you are in heaven! No subs needed.
Try some Chineese based on EL84 tubes...
Solid state.... I don't like cheap solid state...may be NAD, some British electronics - again 50 wpc is enough

KING OF THE MONITORS: DYNAUDIO!

They really are impressive. Check out the 140's or the 52SE's. HUGE bang for the buck. Very neutral, detailed and fun in every sense of the word. I have looked into NHT, Quad 12L, Monitor Audio GR10, but nothing moves me like Dyn does.

I 2nd Rkerv's response. I own a pair of 52SE's too. Just be prepared to feed them with a fair amount of power though.

All good responses. I have a pair of Focal Chorus 806V's that are some of their smaller "bookshelf" speakers and love them.

I also play lossless music- FLAC/SHN off my hardrive through a Linksys Music Bridge and it works excellent. My amp is an ancient Audio Research D-90 Tube/Solid State hybrid with their SP-12 Pre-amp. Also use a Bob Carver
D-8 Dominator Subwoofer that is perfect size for my room and really sounds excellent.

All in all I'm very happy with my system and highly recommend the Focal speakers and Bob Carver Sub. Hard to not like.

I like the Triangle Titus 202.

Easy to drive, sounds great with any kind of music at any volume, front ported to help with the low end you'll need if the shelves sit up high and truly small enough to fit on most any bookshelf. Add a sub later and you have some serious full range sound.