Best used preamp for around $1000. . .

If you like extreme high rez and you already possess a set of high rez speakers, then I recommend a used Spectral DMC-10 for under 1K in excellent shape. Spectral owners tend to be meticulous about their equipment. Plus their service dept. is suberb!! They will tune it up for under 200 bucks. If you like a warmer sound, then stick with cj or ARC, because service will become a factor sometime in a tube component lifetime. If it does not work almost of the time then what is its worth???

BAT VK-3i or SF Line 1, SFL-1/SFL-2. All are extremely transparent.

For the money, a Threshold T3 is a great value.

I haven't heard anyone comment about the Adcom GFP-750. What do people think about it? I've read the reviews, but I would hope to get a plurality of opinions about it. Of course, my ears will be the deciding factor, but thoughtful opinions are always appreciated!!!

If you can find one, I've heard good things about the Musical Design SP2-B. I just picked up a used one for well under your cap and had it sent directly to Musical Designs for a tune up and some tweaking; total still under $1000 including interconnects.