Please keep in mind I am selling one of these but I think the Lehmann Black cube and Plinius Jarrah are the best in that range. I am looking to upgrade though...
About 18 months ago, when I was also looking for very good quality phono preamp in the $500 (used) range, I considered several models and eventually chose the Lehmann Audio Black Cube SE (the model with the much larger power supply). I have been very pleased with the SE's performance in my system. There are 1 or 2 other phono preamps in the $800-1200 (MSRP) that certainly deserve consideration, the Black Cube SE should be on your "short list" to audition. (And DO audition the finalists on your list -- their performance will be highly dependent on the other components in your system.)