What do you think is the best integrated amplifier under 1000

There are many older amps sound excellent. One of my favorites are Sony and Yamaha V-fets. Depends a lot on the type of sound you like and how loud you listen.

A Tandberg 3012 or 3012A is also a great 100 watt integrated too that will run you $4-500.  Also a Creek 5350 SE supposed to be a great sounding unit too.  I had the Creek 4330 many years back and it was a very nice sounding unit.  

Hi,

Really don't know about "the best" as I haven't heard/used more than a half a dozen units, but I've had extensive experience with both Rogue Audio Sphinx v3 and Peachtree Audio 150se, both of which can be found these days for a little less than 1k. 

IMHO, both of these integrated amps are outstanding and offer performance that is way, way above what one expects at their respective price points.  Both  are powerful and authoritative enough to drive Magnepan LRS, notoriously difficult speakers to drive. The Sphinx is really one of the very best amps I've had the opportunity to hear, even on comparison with other much more expensive units. 

In short, I would recommend either one, depending on your budget, associated equipment, sources of music, preferred sound signature, etc. Both are currently available used online... good luck and let us know what you finally acquire.